Raginis was born in Zariņi ("Zariny") village near to Dźwińsk (Daugavpils), Courland Governorate, Russian Empire (present-day Latvia) to a landowning family with patriotic traditions. Soon after graduating from a gymnasium in 1927, he joined the Infantry NCO School in Komorowo near Ostrów Mazowiecka where he was a mediocre student and completed his studies in 1928. He then completed a short practice of the military and the same year he enrolled at the Infantry Officers School in Ostrów Mazowiecka. One of his schoolmates recalled: ""He had a borderland accent, and was quiet and shy. Slim, small, blond hair ... "" After graduating on July 15, 1930, he was assigned to the 76th Infantry Regiment stationed in Grodno, where he was a platoon commander and instructor-lecturer at the School Cadet Corps. In 1939, as a distinction, he was advanced to lieutenant and then to captain and assigned to the elite Border Defence Corps (KOP) as the commander of the 3rd company, heavy machine gun battalion, of the Border Defence Corps Regiment "Sarny" under the command of Lt-Colonel Nikodem Sulik.