He enlisted in the Navy on 16 July 1938 at Miami, Florida, and underwent flight training at the Naval Air Station Pensacola, Fla., before winning his wings on 12 October 1939.
Bull took part in the gallant efforts of Patrol Wing 10[1] (PatWing 10) as its slow, ungainly PBY Catalina flying boats hunted for elements of the Japanese fleet.
On 21 January 1942, a temporary appointment as lieutenant (junior grade) was sent to Bull, but no record of his execution of the oath of office has been found.
Driven off by antiaircraft fire, he persistently remained in the vicinity and, as a result, sighted 26 ships a short time later.
During another reconnaissance flight in the vicinity of the island of Ambon in the Netherlands East Indies on 5 February 1942, Bull searched for an enemy aircraft carrier group reported to be nearby.