Complex sentence: He joined the Anti Aircraft Service of the Territorial Army in 1935 and during World War II he served as Officer Commanding No.5 and then No.6 Balloon Centre preventing German air attacks.
Split into simpler sentences: He joined the Anti Aircraft Service of the Territorial Army in 1935. During World War II he served as Officer Commanding No.5 and then No.6 Balloon Centre preventing German air attacks.