Complex sentence: In October 1937, he became the commander of the 13th Army Corps, that later served in the 1938 German occupation of Sudetenland, for the German invasion of Poland he was appointed head of his own Army Corps "Weichs".
Split into simpler sentences: In October 1937 he became the commander of the 13th Army Corps, that later served in the 1938 German occupation of Sudetenland. For the German invasion of Poland he was appointed head of his own Army Corps "Weichs".