General Ivanov participated in the Russo-Japanese War in 1904, he was appointed to the 1st Manchurian Army. In mid-July 1904, he was appointed commander of the Eastern Detachment, after its commander, Lieutenant General Fyodor Keller was killed at the Battle of Motien Pass, and was later appointed to the 3rd Siberian Army Corps, and commanded the corps during retreating from Liaoyang after the battle ended. Later during the Battle of Shaho, he was ordered to bypass the left flank of the Japanese Army and repulse them back to Korea. After that, the Japanese retreated due to heavy resistance by the Russians. After that at Mukden, he distinguished himself during defending against the Japanese. After that brief success of his, he was awarded the Order of St. George both the 3rd and the 4th class for military distinction.