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.

After graduating from a four-year primary school in Biržai, he enrolled at a private gymnasium of Michail Pavlovsky in Vilnius in 1909.

He planned to study agronomy at the Kyiv Polytechnic Institute, but after the outbreak of World War I he enrolled at the Military Academy in Vilnius.

[1] In November 1918, Ladiga returned to his native village and organized a group of about 150 local men to protect against various roaming gangs of demobilized soldiers.

Several officers, including Ladiga, signed a letter asking to replace regiment's commander Jonas Galvydis-Bykauskas [lt] with someone who showed more enthusiasm and initiative.

[1] Upon learning of this letter, Galvydis-Bykauskas attempted to replace Ladiga with Julius Čaplikas [lt] and challenged them to duel when they refused to follow orders.

[1] After this conflict, Galvydis-Bykauskas was assigned as the director of the War School of Kaunas and Antanas Juozapavičius became the acting commander of the 1st Infantry Regiment.

[4] Under his command, the 1st Infantry Regiment participated in the first organized Lithuanian offensive on 3–8 April 1919 in hopes of capturing Vilnius.

[6] On 17 July 1920, Ladiga commanded the division on its march into Vilnius (then under Soviet control but recognized as Lithuania's territory in the Soviet–Lithuanian Peace Treaty).

[1][2] On 23 August 1920, Ladiga replaced Stasys Nastopka and became the fist assistant minister of defence and the acting commander of the Lithuanian Army.

[2] Ladiga studied at the Military Academy of ETH Zurich in November 1921 – March 1922[2] and War College (Prague) in 1922–1923.

[4] He continued to lead the General Staff until 22 June 1926 (with a month-long break in September–October 1925 due to disagreement with defence minister Teodoras Daukantas).

[6][7] He was removed as the Chief of the General Staff after the election to the Third Seimas was won by the left-wing Lithuanian Popular Peasants' Union and Social Democratic Party of Lithuania.

[4] Ladiga participated in organizing the coup d'état of December 1926 against the government of President Kazys Grinius.

[4] However, he sympathized with the Lithuanian Christian Democratic Party, the main opponents of the authoritarian regime of President Antanas Smetona.

[2] When Lithuania was occupied by the Soviet Union in June 1940, Ladiga was arrested by the NKVD on 12 August 1940.

[14] During World War II, she helped hide and rescue Irena Veisaitė, a Jewish girl from the Kovno Ghetto, for which she was recognized as a Righteous Among the Nations.