Complex sentence: In 1918, he joined the fledgling Royal Air Force Chaplaincy Service, rising through the service to become an Honorary Chaplain to the King and eventually its Archdeacon (Chaplain-in-Chief).
Split into simpler sentences: In 1918, he joined the fledgling Royal Air Force Chaplaincy Service. He rose through the service to become an Honorary Chaplain to the King and eventually its Archdeacon (Chaplain-in-Chief).