Complex sentence: Before he could fully embark on a business career, Shigeta enlisted to serve in the U.S. Marine Corps during the Korean War where he served for 2 1/2 years, and rose to the rank of Staff Sergeant.
Split into simpler sentences: Before he could fully embark on a business career, Shigeta enlisted to serve in the U.S. Marine Corps during the Korean War. He fought in Korea, served for 2 1/2 years, and rose to the rank of Staff Sergeant.