In 1914, Povilas Plechavičius graduated from the Orenburg cavalry war school. During World War I he fought with the Russian army against the German Empire, Austria-Hungary and the Ottoman Empire. During the war, he was wounded three times. In October 1917, he and his brother, Aleksandras, were on the southern Front against the Ottomans. On news of the outbreak of the Lithuanian–Soviet War, both of them illegally left their regiments for Samogitia.