Upon graduating from the Military Academy in Vilnius, Ladiga served in the Imperial Russian army during World War I and earned the rank of captain. He returned to Lithuania in 1918 and volunteered to the newly formed Lithuanian army. He was appointed as the commander of one of the battalions of the 1st Infantry Regiment. Ladiga quickly rose through the ranks and commanded the Vilkmergė Group in the Lithuanian–Soviet War. He also led units against the Bermontians and in the Polish–Lithuanian War. After an unsuccessful campaign in September 1920, Ladiga resigned field office and joined the General Staff in Kaunas. After the Lithuanian Wars of Independence he continued military studies in Switzerland and Czechoslovakia. He rose to the rank of a general and briefly served as the Chief of the General Staff in 1925–1926. He was forced to retire from active military duty after the military coup of December 1926.