Vũ Văn Dũng

At first, Vũ Văn Dũng was subordinate of Phạm Ngô Cầu (the administrator of Phú Xuân appointed by Trịnh lord). In 1786, Tây Sơn army captured Phú Xuân, he surrendered to Nguyễn Huệ. He was granted the position Đại tư khấu (大司寇 "Grand Minister of Justice"). Later, he was sent to Tonkin to enlist rebel soldiers by offering amnesty.

After Nguyễn Quang Toản ascended the throne, the regent Bùi Đắc Tuyên, replaced him with Ngô Văn Sở, and called him back to Phú Xuân. On the way to Phú Xuân, he was persuaded by Trần Văn Kỷ to stage a coup against Tuyên. Vũ Văn Dũng, Phạm Công Hưng and Nguyễn Văn Huấn, besieged Tuyên's house, arrested him, and threw him into prison. Dũng then ordered Nguyễn Quang Thùy to arrest Ngô Văn Sở in Tonkin; In the same time, Huấn was sent to Quy Nhơn to arrest Bùi Đắc Trụ (son of Tuyên) in Quy Nhơn.

Sở and Trụ were taken to Phú Xuân, and thrown into Perfume River together with Tuyên. The younger emperor could do nothing but weep. After the coup d'état, general Trần Quang Diệu retreated from Diên Khánh, and marched north. Finally, Diệu stayed at An Cựu. An army under Vũ Văn Dũng and Nguyễn Văn Danh also marched there to defense. A civil war might break out at any moment, which made the young emperor afraid.

Later, the crisis was settled by mediation of Phạm Công Hưng; Diệu was persuaded to reconcile with Dũng, and came back to Phú Xuân. Dũng was granted the position Đại tư đồ (大司徒 "Grand Minister Over the Masses"), and became one of regents together with Trần Quang Diệu, Nguyễn Văn Huấn, and Nguyễn Văn Danh.[1][2]

Nguyễn Ánh besieged Quy Nhơn in 1799. He was sent to reinforce together with Trần Quang Diệu. When marched to Thạch Tân, they found the road was blocked by Nguyễn Văn Thành and unable to reach there. The army under Dũng stayed at Chung Xá. In the night, a soldier saw a sambar deer pass by, and shouted: "con nai!" (a sambar deer!) It was misheard as "quân Đồng Nai!" (army of Đồng Nai!) by other soldiers, and shouted everywhere. The Tây Sơn army melted away in all directions, and was pursued by the Nguyễn army. Though they used to be political opponents, Trần Quang Diệu finally decided to conceal the fact. Dũng was thankful, and made friends with him.[1]

Hearing the news of defeat, Quy Nhơn surrendered to Nguyễn lord, its name was changed to Bình Định. Diệu and Dũng stayed at Quảng Nam. Trần Viết Kết and Hồ Công Diệu, spoke evil of Diệu, so the young emperor ordered Dũng to kill Diệu. But, Dũng showed the letter to Trần Quang Diệu. Trần Quang Diệu marched to Phú Xuân, the young emperor had to arrest Trần Viết Kết and Hồ Công Diệu and transferred them to Trần Quang Diệu.[2]

In 1800, an army under Trần Quang Diệu besieged Bình Định. In the same time, a navy led by Dũng sealed the Thị Nại Port. Getting this information, Nguyễn Ánh led a navy to reinforce Bình Định. In January 1801, Nguyễn army reached Thị Nại Port. Two Nguyễn generals, Võ Di Nguy and Lê Văn Duyệt, were vanguards to attack Tây Sơn navy. Võ Di Nguy was killed in action; Lê Văn Duyệt fought bravely, and set fire to Tây Sơn naval vessels. Dũng had to abandoned Thị Nại Port, and joined Diệu's army.

Nguyễn Ánh left Nguyễn Văn Thành to fight against Diệu and Dũng, and attacked the capital Phú Xuân directly, and captured it. Diệu and Dũng planned to resumed the capital, but the road was blocked by Lê Văn Duyệt. They had to besiege the citadel more actively. The siege of Bình Định continued for over a year to June 1801, when the citadel's food provisions were exhausted. Võ Tánh, the Nguyễn general guarding the citadel, committed suicide. Tây Sơn army captured the citadel. The citadel was used as a base camp to attack Nguyễn lord.[1][2]

30 thousand men under the young emperor marched south to resume the lost territory, but was utterly beaten in the mouth of Nhật Lệ River. The young emperor fled to Thăng Long. Diệu and Dũng abandoned Quy Nhơn. They retreated to Laos, and planned to march to Nghệ An, then to the destination, Thăng Long.[1] But Nghệ An was also captured by Nguyễn army. Finally, Dũng was captured in Nông Cống District,[2] and transferred to Huế, in where he was beheaded.