The USAAC sent the B17 into the ETO (European theatre of operations) with the idea that being so heavily armed together with its specialised flight formation would enable B17s to fly over enemy territory in daylight without fighter escort - But regretably this policy produced near disastrous results
The B24 was its counterpart - but among many US aircrews it had a reputation for being a heavy difficult a/c to fly - needing constant hands
on controls at all times - Ready to catch any unwary pilot out.
Later in the war the Liberator was converted into the heavily armed
extra long range Privateer PB4y - with extended nose, single high fin
and extra power operated side and nose turrets. Used mostly by
the USN in the Pacific and South Asian waters and war zones.
For every day of WW11 Coastal Command lost one of its airmen.