The Imperial Russian Army was the armed land force of the Russian Empire, founded in 1721 when the Tsardom of Russia became an empire under Peter the Great. Peter the Great was responsible for modernizing the Russian military, and Russia would fight in the Seven Years' War, the wars with the Ottoman Empire and Sweden in the late 18th centuries, the French Revolutionary Wars, the Napoleonic Wars, the Greek War of Independence, the suppression of Polish and liberal Russian uprisings, the Crimean War, the Russo-Turkish War of 1877, the Boxer Rebellion, the Russo-Japanese War, and World War I.
The army was led by aristocratic officers, and its ranks were swelled with peasants. By 1850, the army had a strength of 900,000 regulars and 250,000 cossacks (irregulars), and the army could field a very large army during times of war, although many of these troops would die in battle due to Russia's tendency to use "human wave" tactics. World War I led to the collapse of the Russian army after many failed offensives, and the army would be divided between the aristocratic and anti-revolutionary White Army and the communist and workers' Red Army. The Russian Civil War would see former czarist officers and soldiers fight on opposite sides, and the Red Army would ultimately succeed the Imperial Russian Army as the armed forces of Russia, now known as the Soviet Union.