Complex sentence: It was ended by the Polish government in March 1920 and its fate was sealed by the Treaty of Saint Germain, which gave Galicia west of the San to Poland and by the Peace of Riga in 1920.
Split into simpler sentences: It was ended by the Polish government in March 1920. Its fate was sealed by the Treaty of Saint Germain, which gave Galicia west of the San to Poland, and by the Peace of Riga in 1920.