Complex sentence: During the Japanese occupation of Hong Kong beginning in 1941, most of the personnel at the school, including then-Headmaster Gerald Goodban were imprisoned, and the school building itself transformed into a military hospital for soldiers of the Imperial Japanese Army.
Split into simpler sentences: During the Japanese occupation of Hong Kong beginning in 1941, most of the school personnel, including then-headmaster Gerald Goodban, were imprisoned. The school building was transformed into a military hospital for soldiers of the Imperial Japanese Army.