“I have a friend who is adamant that the P-47 (Thunderbolt) broke the back of the Luftwaffe before the P-51(Mustang)”

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May I rephrase the premise? Assuming the 8th USAAF Air Force fighter force played a major role in crippling the LUFTWAFFE, which of its fighters played the most important role?

If this is the question, I heartily agree with your friend. By April 1944 the LUFTWAFFE could offer effective resistance against the 8th Air Force on only an intermittent basis and at heavy cost. Had the 8th not switched to tactical targets it could have ruined German fuel and industrial production in May 1944 as effectively as it did in August 1944. Even in March 1944 the LUFTWAFFE was capable of effective resistance only sporadically against deep targets such as Berlin.

My analysis above suggests that the LUFTWAFFE fighter defense was already in serious trouble by at least the end of February 1944. If that is the correct date of the “broken back” then further analysis of the question becomes fairly simple. First, prior to that date the outstanding characteristic of the P-51 vs. P-47, its additional range, was hardly a factor. Second, during that period P-51s were encountering many teething troubles (particularly gun failures) which limited their effectiveness. Third, the number of P-51s available was a small fraction of the total 8th Air Force fighter force.

The first P-51 escort group was the 9th Air Force’s 354th (attached to 8thAF) which flew missions from 5 December 1943 and was quite effective in January-February 1944. The 8th Air Force’s first P-51 group was the 357th operational from 11 February 1944. They claimed only 21 victories during February 1944. The 4th Fighter Group only flew its first P-51 mission on 25 February 1944. By February 1944 there were three P-38 groups in the 8th Air Force. They had a long range but were barely holding their own against the LUFTWAFFE. The backbone of the 8th Air Force fighter force through the end of March 1944 was the P-47D.

In late 1943 the P-47D with water injected engines and broad “paddle blade” props began to fly with the 8th Air Force. With these modifications the high altitude speed and most importantly the climb rate of the P-47 improved significantly. When 4th Fighter Group pilots flew their first P-51Bs against these improved Thunderbolts in mock combat they wondered whether they had actually received a superior aircraft. This from the 4th Fighter Group which was prejudiced against the Thunderbolt!

There are so many “Mustang-lovers” (what a pretty airplane!) it will be hard to convince anyone but I for one agree with your friend.