As Siemienowicz wrote, he was fascinated by artillery since childhood, and he studied many sciences to increase his knowledge (mathematics, mechanics, hydraulics, architecture, optics, tactics). In 1632–1634 he took part in the Smolensk War, in the Siege of Belaya under Mikołaj Abramowicz (who in 1640 became the first Lithuanian General of Artillery). It is possible that in 1644 he took part in the Battle of Ochmatów.