Complex sentence: When America was drawn into the Second World War, Michael enlisted in the U.S. Army Air Corps, becoming a pilot, but on the day of his 23rd birthday, as he brought his plane into land, the hangar he was entering blew up.
Split into simpler sentences: When America was drawn into the Second World War, Michael enlisted in the U.S. Army Air Corps, becoming a pilot. However, on the day of his 23rd birthday, as he brought his plane into land, the hangar he was entering blew up.