Kosciusko, Thaddeus (1746–1817), a Polish army officer and national hero. A devoted fighter for liberty, he helped the American patriots in their struggle for independence during the Revolutionary War and later led an unsuccessful attempt to free Polish territory from Russian control.

Kosciusko was the son of an impoverished nobleman. He received his military training at Warsaw's Royal College and in England, France, and Germany. On his arrival in America in 1776 Kosciusko was commissioned a colonel of engineers. His technical training was of great help to the Continental army. He made an important contribution to the American victory at Saratoga in 1777 and supervised construction of the fortifications at West Point, 1778–80. After the war, Congress made him a citizen and gave him the rank of brigadier general.

Kosciusko returned to Poland in 1784. In 1789 he was made a major general in the Polish army and in 1792 led Polish forces against a Russian invasion that resulted in Poland's defeat and partition. In 1794, after being named leader of a provisional government, he led an insurrection against the Russians. He was wounded in battle and taken prisoner. Kosciusko was released in 1796 and exiled. He returned to the United States and then went to France and Switzerland, where he continued to work for an independent Poland. He was buried as a national hero in Kraków.