During the First Sino-Japanese War, Nishi commanded the IJA 2nd Infantry Brigade during the invasion of the Liaodong Peninsula in Manchuria. In August 1895, he was made a baron ("danshaku") in the "kazoku" peerage system. In May 1896, he was commander of the Japanese occupation forces in Weihaiwei, in Shandong Province of China. Promoted to lieutenant general in October of the same year, he followed Nogi Maresuke as commander of the 2nd Infantry Division. He deployed with the division back to Manchuria in February 1904 at the start of the Russo-Japanese War and participated in the Battle of the Yalu, the capture of Antung, and the Battle of Liaoyang. He was promoted to full general in June 1904 of the same year. In April 1905, he was awarded the Order of the Golden Kite, 1st class. From May 1905, he was head of the Inspectorate General of Military Training, one of the three most powerful posts in the Japanese Army. Nishi was appointed aide-de-camp to the Prince Fushimi Sadanaru on his trip to Europe in 1907, and on his return was elevated to viscount ("shishaku").