Stanisław Ostrowski was born on October 29, 1892, in Lvov, Poland. He studied medicine in Lvov—with partial education in Vienna, Austria—and obtained his medical degree in 1919 in Lvov. When Poland struggled for independence, his other mission was military service. He belonged to Polish patriotic organizations, such as the Riflemen’s Association and the Union of Active Struggle, and graduated from officer school and served as a soldier and medical physician in Joseph Pilsudski’s First Brigade and Medical Chancellery of Legions during World War I. He defended Lvov in 1918 and in 1920 was the chief medical physician of the infantry regiment. In 1920, he was honored with the medal Orlęta (“Eaglets”), a commemorative order for the Lvov defenders against the Soviets.