Complex sentence: KKE members volunteered to fight on the side of the republican government of Spain during the Spanish Civil War of 1936--1939; about 440 Greeks joined the ranks of the International Brigade, many of whom were high-ranking KKE members.
Split into simpler sentences: KKE members volunteered to fight on the side of the republican government of Spain during the Spanish Civil War of 1936--1939. About 440 Greeks joined the ranks of the International Brigade, many of whom were high-ranking KKE members.