Bomber Command was struggling against the improved German air defences . In the first months of the year it was losing over 200 aircraft a month - and over 1500 aircrew killed or captured. In response, American planners intended to lure the Luftwaffe into a decisive battle by launching massive attacks on the German aircraft industry. On February 20th, the USAAF launched a campaign to cripple the Luftwaffe that became known as "Big Week". During the campaign the Luftwaffe lost 355 fighters and its operational strength shrank by 50%. It also lost nearly 100 valuable fighter pilots.

One of the most important developments of "Big Week" was the introduction of the P-51 Mustang escort fighter. It had the range to escort the USAAF bombers to the target and back again, the performance to engage any piston-engine German fighter and the fire power (six .50 calibre machine guns) to destroy them. By March, 1944, squadrons of Mustangs flew "fighter sweeps" ahead of the bomber formations to clear the skies of German planes. Between March and April 1944. 500 Luftwaffe aircraft and 400 pilots were lost in only 10 days of operations. In four months 1,000 German fighter pilots were killed - a quarter of the entire German fighter pilot force.

Unfortunately Mustangs and other long range Allied fighters could not operate effectively on night time missions. Long distance navigation was difficult and it was very hard to spot enemy aircraft in the dark. The Bomber Command aircraft had to fly their missions without the help of any "little angels".