The Battle of Mukden commenced on 20 February 1905. In the following days Japanese forces proceeded to assault the right and left flanks of Russian forces surrounding Mukden, along a 50-mile (80 km) front. Approximately half a million men were involved in the fighting. Both sides were well entrenched and were backed by hundreds of artillery pieces. After days of harsh fighting, added pressure from the flanks forced both ends of the Russian defensive line to curve backwards. Seeing they were about to be encircled, the Russians began a general retreat, fighting a series of fierce rearguard actions, which soon deteriorated in the confusion and collapse of Russian forces. On 10 March 1905, after three weeks of fighting, General Kuropatkin decided to withdraw to the north of Mukden. The Russians suffered a estimated 90,000 casualties in the battle.

The retreating Russian Manchurian Army formations disbanded as fighting units, but the Japanese failed to destroy them completely. The Japanese themselves had suffered heavy casualties and were in no condition to pursue. Although the Battle of Mukden was a major defeat for the Russians and was the most decisive land battle ever fought by the Japanese, the final victory still depended on the navy.