Foreign involvement in the Spanish Civil War

It was then that the Non-Intervention Committee was created to uphold the agreement, but the double-dealing of both the Soviet Union and Germany had already become apparent.[14] The ostensible purpose of the committee was to prevent personnel and matériel reaching the warring parties, as with the Non-Intervention Agreement.[2] The committee first met in London on 9 September 1936.[15][nb 2] It was chaired by the British W. S. Morrison. France was represented by Charles Corbin, Italy by Dino Grandi and the Soviet Union by Ivan Maisky. Germany was represented by Joachim von Ribbentrop, and Portugal, whose presence had been a Soviet requirement, was not represented.[16] The second meeting took place on 14 September.[17] It established a subcommittee to be attended by representatives of Belgium, Czechoslovakia, France, Germany, Italy, the Soviet Union, Sweden and the United Kingdom to deal with the day-to-day running of non-intervention. Among them, however, the United Kingdom, France, Germany and Italy dominated, perhaps worryingly so. Soviet non-military aid was revived but not military aid.[18]

Meanwhile, the 1936 meeting of the League of Nations began.[19] There, Anthony Eden convinced Monteiro to have Portugal join the Non-Intervention Committee.[19] Álvarez del Vayo spoke out against the Non-Intervention Agreement, claiming that it put the rebel Nationalists on the same footing as the Republican government.[20] The Earl of Plymouth replaced Morrison as the British representative.[21][22] A member of the British Conservative Party, he often adjourned meetings to the benefit of the Italians and Germans, and the committee was accused of having an anti-Soviet bias.[22]

On 12 November, plans to post observers to Spanish frontiers and ports to prevent breaches of the agreement were ratified. France and the United Kingdom became divided on whether to recognise Franco's forces as a belligerent, as the British wanted, or to fail to do, as the French wanted.[23] That was subsumed by the news that the Italian and German governments had recognised the Nationalists as the true government of Spain.[23] The League of Nations condemned intervention, urged its council's members to support non-intervention and commended mediation.[24] It then closed discussion on Spain, leaving it to the committee.[25] A mediation plan, however, was soon dropped.[24]

The Soviets met the request to ban volunteers on 27 December, Portugal and did so on 5 January and Germany and Italy on 7 January.[26] On 20 January, Italy put a moratorium on volunteers since it believed that supplies to the Nationalists were now sufficient. Non-intervention would have left both sides with the possibility of defeat, which Germany, Italy and the Soviet Union, in particular, were keen to avoid.[27]

Observers were posted to Spanish ports and borders, and both Ribbentrop and Grandi were told to agree to the plan, significant shipments already having taken place.[28] Portugal would not accept observers but agreed to personnel attached to the British embassy in Lisbon. Zones of patrol were assigned to each of the four nations, and an International Board was set up to administer the scheme. There were Italian assurances that Italy would not end non-intervention.[29]

In May, the committee noted two attacks on the patrol's ships by Republican aircraft.[30] It iterated calls for the withdrawal of volunteers from Spain, condemned the bombing of open towns and showed approval of humanitarian work.[31] Germany and Italy stated that they would withdraw from the committee and from the patrols without guarantees of no further attacks.[30][32] Early June saw the return of Germany and Italy to the committee and the patrols.[33] Attacks on the German cruiser Leipzig on 15 and 18 June made Germany and Italy once again withdraw from patrols but not from the committee.[34][35] That prompted the Portuguese government to remove British observers on the Spanish-Portuguese border.[36] The United Kingdom and France offered to replace Germany and Italy, which, however, believed that they would be too partial.[37] Germany and Italy requested for land controls to be kept and for belligerent rights to be given to the Nationalists to allow rights of search to be used by both the Republicans and the Nationalists to replace naval patrols.[34][37] A British plan suggested naval patrols to be replaced by observers in ports and ships, with land control measures being resumed.[38][39] Belligerent rights would not be granted until substantial progress was made on the volunteer withdrawal.[39]

It culminated in a period during 1937, when all of the powers were prepared to give up on non-intervention. By the end of July, the committee was in deadlock, and the aims of a successful outcome to the Spanish Civil War was looking unlikely for the Republic.[40] Unrestricted Italian submarine warfare began on 12 August.[40] The British Admiralty believed that a significant control effort was the best solution to attacks on British shipping.[41] The committee decided that naval patrols did not justify the expense and would be replaced with observers at ports.[42]

The Conference of Nyon was arranged by the British for all parties with a Mediterranean coastline, despite appeals by Italy and Germany for the committee to handle piracy and the other issues that the conference was to discuss.[43] It decided for French and British fleets to patrol the areas of sea west of Malta and to attack any suspicious submarines.[44] Also, warships that attacked neutral shipping would be attacked.[45] Eden claimed that non-intervention had stopped a European war. The League of Nations reported on the Spanish situation by noting the "failure of non-intervention".[45] On 6 November, the plan to recognise the Nationalists as belligerents, once significant progress had been made, was finally accepted.[46] The Nationalists accepted on 20 November and the Republicans on 1 December. On 27 June, Maisky agreed to send two commissions to Spain to enumerate foreign volunteer forces and to bring about their withdrawal. The Nationalists, wishing to prevent the fall of the sympathetic British government led by Neville Chamberlain, were seen to accept the plan.[47]

Plaque honouring the British soldiers of the International Brigades who died while they defended the Spanish Republic at the monument on Hill 705, Serra de Pàndols.

The British government proclaimed neutrality, and its foreign policy was to prevent a major war by appeasement of Italy and Germany. British leaders believed that the Spanish Republican government was the puppet of extreme-left socialists and communists. Accordingly, the British Cabinet adopted a policy of benevolent neutrality towards the military insurgents, a covert aim being to avoid any direct or indirect help to the Republic. Public opinion was divided, with a clear majority demanding another major war to be avoided. The British establishment was strongly anticommunist and so tended to prefer a Nationalist victory. However, Popular Front elements on the left strongly favoured the Republican cause.[48]

The ambassador to Spain, Sir Henry Chilton, believed that a victory for Franco was in Britain's best interests and so worked to support the Nationalists. British Foreign Secretary Anthony Eden publicly maintained the official policy of non-intervention but privately expressed a preference for a Nationalist victory. Eden also testified that his government "preferred a Rebel victory to a Republican victory".[49] Admiral Lord Chatfield, the British First Sea Lord in charge of the Royal Navy, was an admirer of Franco, and the Royal Navy favoured the Nationalists during the conflict.[50] As well as permitting Franco to set up a signals base in Gibraltar, a British colony, the British allowed the Germans to overfly Gibraltar during the airlift of the Army of Africa to Seville. The Royal Navy also provided information on Republican shipping to the Nationalists, and HMS Queen Elizabeth was used to prevent the Republican navy shelling the port of Algeciras. The German chargé d'affaires reported that the British were supplying ammunition to the Republicans. During the fighting for Bilbao, the Royal Navy supported the Nationalist line that the River Nervión was mined and told British shipping to keep clear of the area, but it was badly discredited when a British vessel ignored the advice, sailed into the city and found that the river was unmined, just as the Republicans had claimed.[50] However, the British government discouraged activity by its ordinary citizens supporting either side.

The Labour Party was strongly for the Republicans, but it was heavily outnumbered by Conservative Party in the British Parliament.[nb 3] the left in France wanted direct aid to the Republicans.[51][52] The Labour Party would reject non-intervention in October 1937.[53] The British Trades Union Congress was split since it had a strong anticommunist faction.[54] Both the British and French governments were committed to avoiding a second world war.[53]

France was reliant on British support in general. Prime Minister, Leon Blum, the socialist leader of the Popular Front, feared that support for the Republic would lead to a civil war and then a fascist takeover of France.[55] In Britain, part of the reasoning was based on an exaggerated belief of both German and Italian preparedness for war.[56]

The arms embargo meant that the Republicans' chief foreign source of matériel was the Soviet Union, and the Nationalists received weapons from Italy mainly and Germany. The last Spanish Republican prime minister, Juan Negrín, hoped that a general outbreak of war in Europe would help his cause by compelling Britain and France to help the Republic at last. Ultimately, neither Britain nor France intervened to any significant extent. The British supplied food and medicine to the Republic but actively discouraged Blum and his French government from supplying weapons. Claude Bowers, the US ambassador to Spain, was one of the few ambassadors friendly to the Republic. He later condemned the Non-Intervention Committee by saying that each of its moves had been made to serve the cause of the rebellion: "This committee was the most cynical and lamentably dishonest group that history has known".[57] Winston Churchill, who initially was an enthusiastic supporter of non-intervention, later described the workings of the committee as "an elaborate system of official humbug".[58]

Following the withdrawal of Germany and Italy from patrols, the French considered abandoning border controls or perhaps leaving non-intervention. However, the French were reliant on the British, who wished to continue with patrols.[34] Britain and France thus continued to labour over non-intervention and judged it effective although some 42 ships were estimated to have escaped inspection between April and the end of July.[59] In trying to protect non-intervention in the Anglo-Italian meetings, which he grudgingly did, Eden would end up resigning from his post in the British Foreign Office.[60] On 17 March 1938, Blum reopened the French border to arms traffic, and Soviet arms flowed in to the Republicans in Barcelona.[61]

Britain and France officially recognized the Nationalist government on 27 February 1939.[62] Labour leader Clement Attlee criticised the way it had been agreed, calling it "a gross betrayal... two and a half years of hypocritical pretense of non-intervention".[63]

The flag of an unidentified unit of the Abraham Lincoln Brigade.

When the Spanish Civil War erupted, US Secretary of State Cordell Hull followed American neutrality laws and moved quickly to ban arms sales to both sides. On 5 August 1936, the United States had made it known that it would follow a policy of non-intervention but failed to announce it officially.[10] Five days later, the Glenn L. Martin Company enquired whether the government would allow the sale of eight bombers to the Republicans; the response was negative. The United States also confirmed it would not take part in several mediation attempts, including by the Organization of American States.[10] US President Franklin Roosevelt initially ruled out US interference publicly with these words: "[there should be] no expectation that the United States would ever again send troops or warships or floods of munitions and money to Europe".[64] However, he privately supported the Republicans and was concerned that a Nationalist victory would lead to more German influence in Latin America.[65]

On 6 January 1937, the first opportunity after the winter break, both houses of the US Congress passed a resolution banning the export of arms to Spain.[66][nb 4] Those against the bill, including American socialists, communists, and even many liberals, suggested that the export of arms to Germany and Italy should be halted as well under the Neutrality Act of 1935 since foreign intervention was a state of war in Spain. Hull continued to doubt the extent of German and Italian operations, despite evidence to the contrary.[67] In 1938, as the tide had turned against the Loyalists, Roosevelt attmpted to bypass the embargo and ship American aircraft to the Republic via France.[68]

The embargo did not apply to nonmilitary supplies, such as oil, gas, or trucks. The US government could thus ship food to Spain as a humanitarian cause, which benefited mostly the Loyalists.[69]

Some American businesses supported Franco. The automakers Ford, Studebaker and General Motors sold a total of 12,000 trucks to the Nationalists. The American-owned Vacuum Oil Company in Tangier refused to sell to Republican ships and at the outbreak of the war. The Texas Oil Company rerouted oil tankers headed for the Republic to the Nationalist-controlled port of Tenerife and illegally supplied gasoline on credit to Franco.[70] Despite being fined $20,000, the company continued its credit arrangement until the war ended. The Republicans spent almost $1 million a month on tires, cars and machine tools from American companies between 1937 and 1938.[71] After the war had ended, José María Doussinague, an undersecretary at the Spanish Foreign Ministry, stated that "without American petroleum and American trucks, and American credit, we could never have won the Civil War".[70]

After the war, several American politicians and statesmen identified the US policy of isolation as disastrous.[72][73] That narrative changed during the Cold War, when Franco was viewed as an ally against the Soviet Union.[74]

Republican propaganda poster stating, "The claw of the Italian invader intends to enslave us".

The Italians provided the "Corps of Volunteer Troops" (Corpo Truppe Volontarie). The use of the troops supported political goals of the German and Italian fascist leaderships, tested new tactics and provided combat experienc so that troops would be prepared for any future war.[75]

The Italian contribution amounted to over 70,000 to 75,000 troops at the peak of the war. The involvement helped to increase Mussolini's popularity. The Italian military aid to Nationalists against the anticlerical and anti-Catholic atrocities that eere committed by the Republicans was exploited by Italian propaganda targeting Catholics. On July 27, 1936 the first squadron of Italian airplanes, sent by Mussolini, arrived in Spain.[76]

The government of Fascist Italy participated in the conflict by a body of volunteers from the ranks of the Italian Royal Army (Regio Esercito), Royal Air Force (Regia Aeronautica) and the Royal Navy (Regia Marina), which were formed into an expeditionary force, the Corps of Volunteer Troops (Corpo Truppe Volontarie, CTV). The maximum number of Italians in Spain fighting for the Nationalists, was 50,000 in 1937.[77] Probably, a total of 75,000 Italians fought in Spain for the Nationalists.[78] Italians also served in the Spanish-Italian Flechas Brigades and Divisions. The airborne component of Aeronautica pilots and ground crew were known as "Aviation Legion" (Aviazione Legionaria) and the contingent of submariners as Submarine Legion (Sottomarini Legionari). About 6,000 Italians are estimated to have died in the conflict.[77] The New York Times correspondent in Seville, Frank L. Kluckhohn, reported on 18 August that "the presence of the Italian destroyer Antonio da Noli here means that an ally has come to help the insurgents".[79]

Mussolini sent massive material aid to Italian forces in Spain that included:

• one cruiser, four destroyers, and two submarines;
• 763 aircraft, including 64 Savoia-Marchetti SM.81 bombers, at least 90 Savoia-Marchetti SM.79 bombers, 13 Br.20 bombers, 16 Ca.310 bombers, 44 assault planes, at least 20 seaplanes, more than 300 Fiat CR.32 fighters, 70 Romeo 37 fighters, 28 Romeo 41 fighters and 10 other fighter planes, and 68 reconnaissance planes;
• 1,801 artillery pieces, 1,426 heavy and medium mortars, 6,791 trucks, and 157 tanks;
• 320,000,000 small arms cartridges, 7,514,537 artillery rounds, 1,414 aircraft motors, 1,672 tons of aircraft bombs and 240,747 rifles.[80]

Also, 91 Italian warships and submarines participated in and after the war, sank about 72,800 tons of shipping and lost 38 sailors killed in action. Italy presented a bill for £80,000,000 ($400,000,000) in 1939 prices to the Francoists.[81]

Italian pilots flew 135,265 hours during the war, partook in 5,318 air raids, hit 224 Republican and other ships, engaged in 266 aerial combats reported to have shot down 903 Republican and allied planes and lost around 180 pilots and aircrew killed in action.

Despite the German signing of a non-intervention agreement in September 1936, various forms of aid and military support were given by Nazi Germany in support of the Nationalists, including the formation of the Condor Legion as a land and air force, with German efforts to fly the Army of Africa to Mainland Spain proving successful in the early stages of the war. Operations gradually expanded to include strike targets, and there was a German contribution to many of the war's battles. The bombing of Guernica, on 26 April 1937, would be the most controversial event of German involvement, with perhaps 200 to 300 civilians killed.[82] German involvement also included Operation Ursula, a U-boat undertaking and contributions from the Kriegsmarine.

The Condor Legion spearheaded many Nationalist victories, particularly in the air dominance from 1937 onward; 300 victories were claimed, as opposed to some 900 claimed by Italian forces.[83] Spain provided a proving ground for German tank tactics as well as aircraft tactics, the latter being only moderately successful. Ultimately, the air superiority, which allowed certain parts of the Legion to excel, would not be replicated because of the unsuccessful 1940 Battle of Britain.[84] The training provided to Nationalist forces by the Germans would prove at least as valuable as direct actions. Perhaps 56,000 Nationalist soldiers were trained by various German detachments in Spain, who were technically proficient and covered infantry, tanks and anti-tank units; air and anti-aircraft forces and those trained in naval warfare.[85]

Probably a total of 16,000 German citizens fought, mostly as pilots, ground crew, artillery men, tankmen, and military advisers and instructors. About 10,000 Germans were in Spain at the peak, perhaps 300 of which were killed.[86] German aid to the Nationalists amounted to approximately £43,000,000 ($215,000,000) in 1939 prices.[86][nb 5] That was broken down in expenditure to 15.5% for salaries and expenses, 21.9% for direct delivery of supplies to Spain and 62.6% for the Condor Legion. (No detailed list of German supplies furnished to Spain has been found.)[86]

Emblem of the Portuguese volunteers "Viriatos".

Upon the outbreak of the civil war, Portuguese Prime Minister António de Oliveira Salazar was officially neutral but favoured the Nationalists.[87] Salazar's Estado Novo held tense relations with the Republic since it held Portuguese dissidents to his regime.[88] Portugal played a critical role in supplying the Nationalists with ammunition and logistical resources.[89]

Direct military involvement involved "semi-official" endorsement by Salazar of an 8,000–12,000-strong volunteer force, the "Viriatos". For the whole war, Portugal was instrumental in providing the Nationalists with a vital logistical organisation and by reassuring Franco and his allies that no interference whatsoever would hinder the supply traffic directed to the Nationalists that crossed the borders of the Iberian countries. The Nationalists even referred to Lisbon as "the port of Castile".[90] In 1938, with Franco's victory increasingly certain, Portugal recognized Franco's regime and, after the war in 1939, signed a treaty of friendship and non-aggression pact, the Iberian Pact.[87] Portugal played an important diplomatic role in supporting Franco, including insisting to British government that Franco sought to replicate Salazar's Estado Novo and not Mussolini's Fascist Italy.[88]

Vatican City

Among many influential Catholics in Spain, mainly composed of conservative traditionalists and people belonging to monarchist groups, the religious persecution was squarely blamed on the Republic. The ensuing outrage was used after the 1936 coup by the propaganda of the rebel faction and readily extended itself. The Catholic Church took the side of the rebel government and defined the religious Spaniards who had been persecuted in Republican areas as 'martyrs of the faith', selectively ignoring the many believing Catholic Spaniards who remained loyal to the Republic and even those who were later killed during the persecution and the massacres of Republicans. The devout Catholics who supported the Republic, included high-ranking officers of the Spanish Republican Army such as the Republican General Vicente Rojo Lluch, as well as the Catholic Basque nationalists who opposed the rebels.[91]

Initially the Vatican refrained from declaring too openly its support of the rebel side in the war, but it had long allowed high ecclesiastical figures in Spain to do so and to define the conflict as a "Crusade". Throughout the war, however, Francoist propaganda and influential Spanish Catholics labelled the secular Republic as "the enemy of God and the Church" and denounced it by holding it responsible for anticlerical activities, such as shutting down Catholic schools, killing of priests and nuns by exalted mobs and desecrating religious buildings.[92]

Forsaken by the Western European powers, the Republicans depended mainly on Soviet military assistance, which played into the hands of the Nationalists, who portrayed the Republic as a "Marxist" and godless state in Francoist propaganda. Its only other official support was from the anti-Catholic and nominally-revolutionary Mexico. By means of its extensive diplomatic network, the Holy See used its influence to lobby for the rebel. During an International Art Exhibition in Paris in 1937 in which both the Nationalist and the Republican governments were present, the Holy See allowed the Nationalist pavilion to display its exhibition under the Vatican flag although the Nationalist flag was still not officially recognised.[93] By 1938, Vatican City had already officially recognised Franco's Spanish State and was one of the first countries to do so.[94]

Regarding the position of the Holy See during and after the war, Manuel Montero, a lecturer at the University of the Basque Country, commented on 6 May 2007:[95]

The Church, which upheld the idea of a 'National Crusade' in order to legitimize the military rebellion, was a belligerent part during the Civil War, even at the cost of alienating part of its members. It continues in a belligerent role in its unusual answer to the Historical Memory Law by recurring to the beatification of 498 "martyrs" of the Civil War. The priests executed by Franco's Army are not counted among them.... In this political use of granting religious recognition one can perceive its indignation regarding the compensations to the victims of Francoism. Its selective criteria regarding the religious persons that were part of its ranks are difficult to fathom. The priests who were victims of the republicans are "martyrs who died forgiving", but those priests who were executed by the Francoists are forgotten.

Volunteer troops from other countries fought with the Nationalists but only a few as national units. Among the latter were Eoin O'Duffy's 700-strong Irish Brigade and the 500-strong French Jeanne d'Arc company of the Spanish Foreign Legion, which was formed mostly from members of the far-right Croix de Feu. Also, 8,000 Portuguese, known as Viriatos, fought for Franco although never as a national unit. Another 1,000 volunteers from countries as diverse as Spanish Guinea, the Philippines, the United States, Brazil, Norway, Belgium, the United Kingdom and Australia fought for the Nationalists.[96] In 1937, Franco turned down separate offers of national legions from Belgium, Greece, and exiled White Russians that had been made by foreign sympathisers.[97]

Ion Moța, the Romanian deputy leader of the Legion of the Archangel Michael (or Iron Guard), led a group of seven Legionaries who visited Spain in December 1936 to ally their movement to the Nationalists by presenting a ceremonial sword to survivors of the Siege of Alcazar.[98] In Spain, the Legionaires decided, against the orders that had been given to them in Bucharest, to join the Spanish Foreign Legion. Within days of joining, Moța and Vasile Marin, another prominent Legionary, were killed on the Madrid Front at Majadahonda.

After the extravagant and widely-publicised funerals of Ion Moța and Vasile Marin, they became a prominent part of the Legion's mythology.[99]

The Norwegian writer Per Imerslund fought with the Falange militia in the war in 1937.

The British journalist Peter Kemp served as an officer with a Carlist battalion for the Nationalists and was wounded.

The St. Patrick's saltire flag of the National Corporate Party, an Irish fascist movement that dispatched the Irish Brigade to support the Nationalists and fight against the Republicans.

Despite the declaration by the Irish government that participation in the war was illegal, around 700 of Eoin O'Duffy's followers ("The Blueshirts") went to Spain to fight on Franco's side. Both sides were former IRA members.

On its arrival, however, O'Duffy's Irish contingent refused to fight the Basques for Franco since it saw parallels between its recent struggle and Basque aspirations of independence. It saw its primary roles in Spain as fighting against communism and for fascism and defending Catholicism.

Anticlericalism and the murder of 4,000 clergy and many more nuns by the Republicans made many Catholic writers and intellectuals cast their lot with Franco, including Evelyn Waugh, Carl Schmitt, Hilaire Belloc, Roy Campbell, Giovanni Papini, Paul Claudel, J. R. R. Tolkien and those associated with the Action Française. Others, such as Jacques Maritain, François Mauriac and Georges Bernanos, initially supported Franco but later grew disenchanted with both sides.

Many artists with right-wing sympathies, such as Ezra Pound, Gertrude Stein, Wyndham Lewis, Robert Brasillach and Pierre Drieu La Rochelle voiced support for the Nationalists. Brasillach collaborated with Maurice Bardèche on his own Histoire de la Guerre d'Espagne and the protagonist in Drieu La Rochelle's novel Gille travels to Spain to fight for the Falange. Lewis's The Revenge for Love (begun 1934) details the anarchist-communist conflict in the years preceding the war and though it is not a Spanish Civil War novel, it is often mistaken for one.

• The Portuguese furnished about 8,000 troops for the Nationalists, known as Viriatos after the Viriatos Legion (Legião Viriato).[100]
• About 500 Frenchmen fought for the Nationalists, most in the Jeanne d'Arc company of the Spanish Foreign Legion.[101]
• Over 1,000 volunteers from other nations served in the Nationalist forces, including Filipinos, Britons, Finns, Norwegians, White Russians, Americans, Belgians, and Turks.[101]
• Probably 75,000 Moroccan Regulares fought in the Nationalist ranks.[102] Spanish Morocco was then an independent protectorate and so the Moroccans were not Spanish citizens. They were feared by the enemy and the local civilian population because they spared no one and "killed everyone", according to an interview with a Moroccan veteran.[103] According to Professor Balfour, "The Moroccan troops involved felt they were fighting a jihad against atheists and communists. Another motivation was money and gaining a foothold in the (Iberian) peninsula".[104][105]
• Despite its name, the Spanish Foreign Legion, which fought for the Nationalists, had mostly Spanish citizens.[106]

Due to the Franco-British arms embargo, the Republican government could receive material aid and purchase arms only from the Soviet Union. To pay for the armaments, the Republicans used US$500 million in gold reserves. At the start of the war, the Bank of Spain had the world's fourth-largest reserve of gold, about US$750 million, despite some assets being frozen by the French and the British governments. The Soviet Union also sent more than 2,000 personnel, mainly tank crews and pilots, who actively participated in combat, for the Republicans.[107] Other countries aided the Republicans by selling weapons and providing volunteer military units. Throughout the war, the efforts of the Republican government to resist the Nationalists and their foreign supporters were hampered by Franco-British 'non-intervention', the long supply lines and the intermittent availability of weapons of widely variable quality. The Franco-British naval embargo allowed Germany and Italy to reinforce their armies in Spain and hampered only Soviet efforts to arm the Republicans.

According to an official Soviet source, more than 2000 Soviet citizens served in Spain, many of them being awarded the Soviet honours and 59 being awarded the title Hero of the Soviet Union.[108] The maximum number of Soviets in Spain at any time is believed to have been 700, and the total during the war is thought to have been between 2,000 and 3,000. Estimates for the pilots of Spanish Republican Air Force from the Soviet Union who took part in the conflict are given at 1,000.[109]

The Republic sent its gold reserve to the Soviet Union to pay for arms and supplies. The reserve was worth $500,000,000 in 1939 prices.[110] In 1956, the Soviet Union announced that Spain still owed it $50,000,000.[81] Other estimates of Soviet and Comintern aid totaled £81,000,000 ($405,000,000) at 1939 values. The German military attaché estimated that Soviet and Comintern aid amounted to the following:

• 242 aircraft,
• 703 pieces of artillery,
• 731 tanks,
• 1,386 trucks,
• 300 armored cars
• 15,000 heavy machine guns,
• 500,000 rifles,
• 30,000 sub-machine guns,
• 4,000,000 artillery shells,
• 1,000,000,000 machine gun cartridges,
• over 69,000 tons of war materiel, and
• over 29,000 tons of ammunition.[111]

Much of the material was purchased in France, Czechoslovakia, the United States, the United Kingdom and Mexico.[112] The Republic was continuously swindled and shortchanged in its purchases.[113]

The Republic also made poor choices in buying ammunition. The arms trade has a standard that with every rifle, 1,000 rounds of ammunition are included; with every machine gun, 10,000 rounds are included; and with every artillery piece, 2,400 shells are included to prevent the hardware from becoming useless by a lack of ammunition. However, many of the purchases fell far short of that standard.[114]

Soviet foreign policy considered collective security against German fascism to be a priority,[115] and the Comintern had agreed a similar approach in 1934.[116] It walked a thin line between pleasing France and not being seen to hinder both the world revolution and communist ideals. It was also the time of the first significant Soviet trials of the Old Bolsheviks.[11] The Soviet press and opposition groups were entirely against non-intervention.[13]

The Mexican government supported fully and publicly the claim of the Spanish Republican government. Mexico refused to follow the non-intervention proposals of France and Britain. Mexican President Lázaro Cárdenas saw the war as similar as the Mexican Revolution although much of Mexican society wanted a Nationalist victory.

Mexico's attitude was an immense moral comfort to the Republic, especially since major Latin American governments (Argentina, Brazil, Chile and Peru) sympathised more or less openly with the Nationalists. However, Mexican aid could mean relatively little in practical terms since the French border was closed and the German, Italisn and Portuguese dictators remained free to supply the Nationalists with a quality and a quantity of weapons that was far beyond the power of Mexico, which could furnish only $2,000,000 in aid[117] and provide only some material assistance, which included rifles, food and a few American-made aircraft, such as the Bellanca CH-300 and the Spartan Zeus, which had served in the Mexican Air Force.

On 21 August 1936, France signed the Non-Intervention Agreement.[118] However, Blum's government provided some aircraft to the Republicans by covert means. Potez 540 bomber aircraft (nicknamed the "Flying Coffin") by Spanish Republican pilots[119] Dewoitine aircraft and Loire 46 fighter aircraft were sent from 7 August to December 1936 to Republican forces.[120] The French also sent pilots and engineers to the Republicans.[121] Also, until 8 September 1936, aircraft could freely pass from France into Spain if they had been bought in other countries.[122]

Research conducted by Gerald Howson after the collapse of the Iron Curtain showed that Poland was second, after the Soviet Union, in selling arms to the Republic. In the autumn of 1936, Poland was the only nation to offer arms to the Republic in any quantity, according to Howson. At the time, the Republic was in great need since the Nationalists were threatening Madrid.[123]

Other countries selling arms to the Republicans included Czechoslovakia and Estonia.[124] Also, $2,000,000 came from the United States for humanitarian purposes.[117]

American veterans displaying the brigade's banner in 1967

Volunteers from many countries fought in Spain, most of them on the Republican side. About 32,000[125] men and women fought in the International Brigades, including the American Lincoln Battalion and the Canadian Mackenzie–Papineau Battalion, which were organised in close conjunction with the Comintern to aid the Spanish Republicans. Perhaps another 3,000[125] fought as members of the Confederación Nacional del Trabajo (CNT) and the Workers' Party of Marxist Unification (POUM) militias. Those fighting with POUM most famously included George Orwell and the small ILP Contingent. While not supported officially, many American volunteers such as the Abraham Lincoln Brigade fought for the Republicans.

"Spain" became the cause célèbre for the left-leaning intelligentsia across the Western world, and many prominent artists and writers entered the Republic's service. As well, it attracted a large number of foreign left-wing working-class men for whom the war offered not only idealistic adventure but also an escape from Great Depression unemployment. Among the more famous foreigners participating on the Republic's side was George Orwell, who went on to write about his experiences in Homage to Catalonia. Orwell's novel Animal Farm was loosely inspired by his experiences and those of other members of POUM at the hands of Stalinists when the Popular Front began infighting, and his experiences also inspired the torture scenes in his Nineteen Eighty-Four. Ernest Hemingway's novel For Whom the Bell Tolls was inspired by his experiences in Spain. George Seldes reported on the war for the New York Post. The third part of Laurie Lee's autobiographical trilogy, A Moment of War, is also based on his Civil War experiences. Norman Bethune used the opportunity to develop the special skills of battlefield medicine. As a casual visitor, Errol Flynn used a fake report of his death at the battlefront to promote his movies. In the Philippines, a pro-Republican magazine, Democracia, had writers, including antifascist Spaniards, Filipino-Spaniards and Filipino progressives such as Pedro Abad Santos, the chairman of the Socialist Party of the Philippines, and Bishop Gregorio Aglipay, of the Philippine Independent Church.[126]

Polish volunteers fighting for the Republic.

Probably 32,000 foreigners fought in the communist International Brigades An estimated 3,000 volunteers fought in other Republican forces during the conflict. Additionally, about 10,000 foreigners participated in medical, nursing and engineering capacities.[127]

The International Brigades included 9,000 Frenchmen, of whom 1,000 died; 5,000 Germans and Austrians of whom 2,000 died and also about 3,000 from Poland. The second-highest number was from Italy with 3,350 men. Then came the United States (2,800 men with 900 killed and 1,500 wounded) and the United Kingdom (2,000 with 500 killed and 1,200 wounded). There were also 1,500 Czechs, 1,500 Yugoslavs, 1,500 Canadians, 1,000 Hungarians; and 1,000 Scandinavians (about half of whom were Swedes). The rest came from a "claimed" 53 countries, and 800 Swiss volunteered, 300 of whom would be killed.[128] Also, 90 Mexicans participated.[129] It has been estimated that between 3,000 and 10,000 of the volunteers were Jewish.[130][131] About 200 volunteers were from Palestine (of both Jewish and Arab origin).

Approximately a third of Irishmen who fought for Republicans died, the group being primarily socialists, trade unionists, and former IRA members. The "Connolly Column" of the International Brigades was named after the Irish socialist leader who had been executed by the British after the 1916 Easter Rising, James Connolly.