Jaroslav Hašek was a Czech anarchist, writer and satirist who is best known for his novel The Good Soldier Švejk, a satirical dark comedy set during the World War I. It is considered one of the first anti-war novels and had enormous influence on the genre, including on the famed novel Catch-22 by Joseph Heller.
The correct pronunciation of Jaroslav Hašek in Czech is Yah-roh-slaf Hah-shek.