After graduating from the famous Corps of Cadets in Warsaw, he joined the Polish Army as a lieutenant during the 1794 Kościuszko Uprising.
After its suppression and the dismemberment of Poland by Russia, Prussia, and Austria, Sowiński's regiment was drafted into the Prussian army.
In 1807, he fought at the Battle of Eylau and received the highest Prussian military decoration, the Pour le Mérite.
During the Russian assault on Warsaw on 6 September 1831, Sowiński personally commanded the defense of the Polish capital's western approaches.
[citation needed] According to recent historians, he was bayonetted to death by the Russians just after the surrender negotiations, who publicized a story that he had been killed at his post in combat.