B/W Pic - Strategic Bombing National Archives

During World War Two USAAF strategic bombing doctrine rode on the
theory of "precision bombing" carried out during the day in spite of
ample evidence to the contrary suggesting daylight bombing was a
recipe for disaster. The Americans doggedly believed bombers flying at
day could not only hit their target but that attempting to fight during
the day was preferable because of the increased accuracy daytime
bombing offered and the alleged survivability inherent in the heavily
armed American bombers.

The USAAF thus turned its workhorse four engine bombers, the B-17
and B-24 bombers, into airborne battleships. Each bomber crew
comprised at least 10 men, in order to wield the heavy defensive
firepower as well as perform the primary bomb delivery task. The B-17
four-engine bomber was a particularly imposing weapon system with
its rugged airframe and 10 heavy machineguns spread around the
plane with the guns located: in tandem in turrets on top of the
fuselage, in the tail, under the plane, and single machine guns on
each side of the bomber's main fuselage.

In spite of the USAAF's belief in the heavy bomber flying during the
day 1943 was a brutal year for US bomber crews. It was only when
American fighter escorts acquired the range to accompany the big
four engine bombers to the target that the daylight part of the
strategic bombing effort began to bear fruit for the Allies.

Picture Courtesy US National Archives, local identifier no.
208-EX-249A-27