Complex sentence: At the start of World War II, Catton was too old for military service and, starting in 1941, served as Director of Information for the War Production Board and later held similar posts in the Department of Commerce and the Department of the Interior.
Split into simpler sentences: At the start of World War II, Catton was too old for military service. In 1941, he took a position as Director of Information for the War Production Board, and later he held similar posts in the Department of Commerce and the Department of the Interior.