Battle of Banja Luka

On 20 July, the Austrian army moves toward Jurkovići. This is the first significant battle with the Bosniak army, commanded by Sali Aga. Sali Aga had three groups (of 1,000, 2,000 and 5,000 troops), which surprised the Austrians. Sali Aga fought Muffling face-to-face: they hurt each other; Salih passed away immediately, while Muffling succumbed two days later. The Austrians won.

Two formations of the Austrian army – one under the command of Field Marshal Goldy and the other under Hildburghausen – joined in front of Banja Luka on 27 July. One kilometer from the Banja Luka fortress, the Austrian army raises a camp. Hildburghausen is demanding that the city be surrendered unconditionally, which the defense refusing it. The siege of the city begins, and after three days the Austrians regroup forces and on 27 July they begin artillery firing at the fort. Between 27 July and 4 August, approximately 1,800 shells were fired daily.

The defense of Banja Luka was commanded by Mehmed Bey Ćatić; in the early days, the defenders gave strong resistance to the Austrian army. The cannon gunners of the Austrian army did not aim precisely and the cannons were moving forward, the city center being fired, forcing the civilian population to retreat deep into the underground walls.

Hildburghausen sends a letter to Captain Ćatić demanding that he surrenders:

"To Pasha, who showed great effort in safeguarding the fortress of Banja Luka, to the officers who along with him find themselves obsessed with the fort and the brave fighters, greetings with good wishes. The obligation of friendship requires us to warn you because you have become aware of the forces of the Imperial army and equipment. So far, you have put a lot of effort into enduring what came there for you. As much you put in your strength and heart, there is that much. But, know, after that, whatever effort you make to preserve the fort – it will be vain work. Your effort is not enough to resist us, it will not really help you. With your Pasha, whose help you hope for, there are three thousand soldiers. I, at this moment, have four experienced generals. It is sufficient that any of they come out before your Pasha. There is no way he can resist it. Now one of our units is preparing against Bužim fortress and the other strong unit, with many army, besieges the fort of Cetingrad. News will arrive today or tomorrow that they passed into our hands. In addition, to a large and powerful army of emperors the commander is Prince of Lorraine, who is tasked with occupying the Ottoman lands in Rumelia. These days, he and his army are leaving Belgrade to occupy Niš, and then he should go and take Vidin. To know about this condition, now certificates were received from that side by one special tap. If you want to we send them to convince you... And so there's no way [for you] to save yourself, whatever you do, we will take away the fort from you. You are trying in vain to prolong the destruction of people. All left you have to do is to give the fort to us, so that we can confidently point you where you want, with your heads, souls and property. Unless you listen to our words and are persistent and stubborn, we will kill you all and crush your root. Don't say you didn't know."

Ćatić's officers declared they would not surrender and Hildburghausen received an answer:

"The fort belongs to a bright, powerful, noble Islamic Padshah, who attained the grace of God. Our blessed fortress, which under its the umbrella protects our children, the homeland left over from our grandfathers, we do not give by our hands to the enemy. We have a solid heart decision for this way, to sacrifice souls and lives for Islam and while there is anyone alive among us, we will not give up the fight."

After the Austrians received news that Hekimoğlu Ali Pasha had set off with 15,000 troops to help the Banja Luka people, the city was even more heavily targeted. Ćatić sent a letter to the Travnik vizier, which was carried through enemy lines by disguised Bosniak soldiers. However, the letter did not reach the meadow vizier because they had already met the army of Hekimoğlu Ali Pasha and it had been handed over to him.

On 3 August, Hildburghausen's scouts are informed that unknown soldiers were spotted in the surrounding woods; he makes the fatal decision not to follow it further. This enabled the Bosniak army to approach the Austrian camp unnoticed.

Hildburghausen expected (though he misjudged the time) that help would be given to the Bosniak army, and he regrouped the soldiers. Field Marshals Succoi and Rommer guarded the right wing while Major General Baranyay shifted the artillery to the left bank of Vrbas. A considerable number of soldiers were left in reserve.

While the Austrians regrouped, the defense troops did the same.

The right wing of the army, which came to the aid of the defenders, was commanded by Krajina Captain Mehmed Bey Fidahić; 4th sanjak of the Bosnian eyalet is placed on the left wing. Among the soldiers were ulema, muderis, etc. There were also Orthodox people faithful to the Bosnian Eyalet and Franciscans who provided material assistance to the army.

Prior to the arrival of assistance, the ratio of attackers to defenders was about 3 to 1; the Austrian army had about 17,000 and the Bosniak had 5,000.

As soon as troops under the command of Hekimoğlu Ali Pasha attacked the Austrian army on the morning of 4 August, the defenders began to attack on the left bank of the Vrbas. Austrian troops, under the command of Baranyay, repel the onslaught of defenders. During the battle, the Austrian officers deviate from the schedule set by Hildburghausen, thereby unknowingly assisting the defenders; a big mistake was made by Baranyay for not deploying infantry. One part of the Austrian army was in keeping with the original order, so a disturbance was caused in their ranks, and it was not possible for the team to establish a single infantry line. Bosniak cavalry uses this and attacks the Austrian army center, causing them great losses.

When the defenders manage to occupy the pontoon bridge, the Austrian troops on the left bank of the Vrbas begin to retreat. Mehmed Pasha, who noticed this, attacked with fierce Austrian troops who were still resisting.

Hildburghausen orders his troops to reinforce the left bank of the Vrbas, thereby aiding Baranyay. This move by Hildburghausen was later regarded as a major mistake of his, as it turned out that Baranyay was strategically incapable and unable to use reinforcement.

The Austrian army on the left bank of the Vrbas is trying to escape by crossing the river; many were non-swimmers and drowned in the waves. Five soldiers each held the horses' tail to cross the river. The right wing provided even more resistance; defense attorneys made five attacks during the day. On the evening of 4 August, Hildburghausen orders a withdrawal.

Mehmed Ali-Pasha orders on 5 August to go after the Austrians. Since the Bosniak troops went partly unorganized in the pursuit, 500 soldiers lose near Klašnica when they reached the Austrian troops. On 13 August, Hildburghausen arrived in Slavonska Gradiška, where he awaited the rest of the army until 20 August.

About 600 defenders were killed, while the Austrian army lost about 300 troops in the direct combat. An unknown number of Austrian soldiers are estimated to have drowned in Vrbas alone from the Hildburghausen camp of 1,000. At least 1,200 soldiers were wounded.

The Bosniak army seized 12 cannons, 315 tents, thousands of barrels, and many rifles, sabers and other military equipment.

The Croatian ban Josip Esterházy, who left Bužim after the defeat of the Austrian army, explained the defeat by the lack of heavy artillery. Austrian officers cited lack of discipline among soldiers as the main reason.