Complex sentence: Cazalet was commissioned into the Queen's Own West Kent Yeomanry in 1915 and reached the rank of Captain, and serving in the front line during World War I, won the Military Cross for gallantry in 1917.
Split into simpler sentences: Cazalet was commissioned into the Queen's Own West Kent Yeomanry in 1915 and reached the rank of Captain. After serving in the front line during World War I, he received the Military Cross for gallantry in 1917.