Jonas Žemaitis was born in Palanga on March 15, 1909, into the family of Jonas Žemaitis and his wife Petronėlė Daukšaitė.
Although his father was a free-thinker, he was christened in the church of Palanga.
From 1910 to 1917, he lived together with his parents in Łomża, Poland. After returning to Lithuania in 1917, the family settled down in the village of Kiaulininkai, Šiluva region.
In 1921, he graduated from first grade of the Raseiniai gymnasium.
In 1926, he enrolled into Kaunas Military School.
After graduation in 1929, he was assigned to 2nd Artillery Regiment, 1st Howitzer Battery, in Kėdainiai.
In 1936, he was sent to France to study at the artillery training school at Fontainebleau. He returned in the summer of 1938, was raised to captain and appointed commander of the 1st Artillery Regiment Division.
In 1940, he was taken into the 29th Corps of Riflemen. Jonas Žemaitis married Elena Valionyte.
In 1941, they settled down in Kaunas where first son Laimutis was born.
After going back to his native region of Šiluva, he headed the Šiluva agricultural cooperative until 1944 (he did not join any Nazi-formed units).
During the years of German occupation, he was active in the underground paramilitary organization of riflemen Laisvės Šauliai.
In 1944, he formed a unit of 150 men from Šiluva and Tytuvėnai and joined the Lithuanian Territorial Defense Force, organized by Povilas Plechavičius, where he was appointed commander of the 310th Battalion.
In 1945, Jonas Žemaitis became a partisan. He fought against the Soviet occupiers until the spring of 1953 when he was arrested and executed in 1954.
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