Siege of Ulsan

The Siege of Ulsan was an unsuccessful Korean and Ming Chinese attempt to capture Ulsan Castle from the Japanese late during the Japanese Invasion of Korea (Imjin War). Korean and Chinese allied forces suffered heavy losses during the siege, and the allied forces were ultimately withdrawn when the garrison sallied forth with the arrival of a relief force.

First Siege of Ulsan
In 1597, the second phase of the Japanese invasion of Korea was launched. After limited progress on land and several naval defeats, Japanese troops withdrew to the southern Gyeongsang province, in which they had set up a defensive perimetre. Without provisions and reinforcements, the Japanese forces had to remain in safety and security of the coastal fortresses (known as wajō) that they controlled. The Japanese commander Katō Kiyomasa had his army stationed in Ulsan, where he had his troops construct a castle. Commanders Yang Hao and Ma Gui led an army of 44,000 Ming troops, and Commander Gwon Yul led an army of 11,500 Korean tropps in a first assault on January 29, 1598. They caught the Japanese army unawared and still encamped, for the large part, outside of Ulsan's unfinished castle walls. The Japanese managed to drive off the attack and withdrew into the castle, but lost 500 men in the process.

A total of around 55,000 troops with the help of singijeons and hwachas then besieged the fortress. The allied force made several assaults on the castle, but all attempts were repulsed by concentrated gun fire. However, the Japanese suffered heavily as well, with more than 600 men being killed and numerous more wounded.

By the tenth day of the siege, the Japanese garrison was on verge of capitulating because of hunger and cold, but reinforcements under the overall command of Mōri Hidemoto came across the river to aid the besieged fortress, threatening the rear of the Chinese and Korean troops.

The Ming commander Ma Gui began to realize the dangerous position of the allied forces, and late on January 3 decided to call off the attack and pull out of the area before the situation deteriorated any further.

However, the calculated retreat quickly broke down and turned into a chaotic rout. The hasty and sudden timing, the heavy rain, the lack of discipline among the troops, and the quickly approaching Japanese forces all contributed to panic. In addition, the chief administrator present at the battle, Yang Hao; left ahead of the troops, which only strengthened the impression that the intended calculated withdrawal was really a chaotic rout.

With the advance of the relief force imminent, and seeing the disorganized withdrawal of the besieging force, the besieged Japanese garrison sallied forth and made a joint attack with the relief force. The allied forces retreated from Ulsan, and the siege of the fortress was suspended.

After the defeat, in May, 1598, the Ming government called General Yang Hao back and sent another army of about 20,000 men led by Liu Ting and a navy of about 13,000 men and 500 battleships led by Chen Lin and Deng Zilong to Korea.

Second Siege of Ulsan
On September 22, 1598, Korean and Chinese allied forces made a second attack against Japanese forces at Ulsan. The alliance army formation was led by Commander Ma Gui, leading an army of 24,000 Chinese. An army of 5,500 Koreans was led by general Kim Eung-seo. Korean and Ming allied forces failed to take the Ulsan Japanese Castle, but unlike the first siege, managed to withdraw in good order.