Complex sentence: George's father died when he was very young leaving him to take care of his mother therefore George was unable to complete high school; he was a cook in the US Navy during the Korean War and also worked as a janitor.
Split into simpler sentences: George's father died when he was very young leaving him to take care of his mother; therefore, George was unable to complete high school. He was a cook in the US Navy during the Korean War and also worked as a janitor.