The battle began with a false retreat that lured the Japanese garrison into a frontal attack. They were defeated with 500 losses and were forced to retreat to Tosan fortress. The allies occupied the city of Ulsan.

On 30 January the allies bombarded the fortress and then took the outer wall of Tosan. The Japanese abandoned much of their food supplies and retreated into the inner fortress. The allies assaulted the inner fortress, at one point even taking a portion of the wall, but suffered heavy casualties.

On 19 February the allied forces attacked again and were repelled. Seeing Japanese reinforcements arrive, Yang Hao decided to lift the siege and retreat, but the disorganized movement led to many stragglers being cut down by the Japanese, leading to heavy casualties.