It's how you win a war. You force unsustainable losses on the other side. This is what happened to the Luftwaffe, particularly at the hands of the US 8th Air Force, but of course operations elsewhere contributed.
Both the British and American strategic bomber forces were able to absorb short term losses at a higher level as long as they kept the long term losses at a level which could be sustained with replacement crews and aircraft (never a serious problem) whilst retaining enough experienced crews. They could withdraw, rest, re-train some units or types and even modify their objectives to keep their losses at a sustainable level without losing the war. The times when the Luftwaffe managed to force such decisions on the Anglo-American bombing forces may, arguably, have extended the war, but they never came close to winning it.
Hindsight is a wonderful thing, not afforded the decision makers at the time, but we can now see that the Luftwaffe never came as close to stopping the Anglo-American strategic bombing campaigns as both sides, but particularly the Germans, thought at the time.
For example the Battle of Berlin, the main part of which was fought between 18/19 November 1943 and 30/31 January 1944 is often cited as a defeat for Bomber Command, probably because the 'Official History' more or less calls it that.
"Thus, Bomber Command was compelled, largely by the German night fighter force, to draw away from its primary target, Berlin, to disperse its effort and to pursue its operations by less efficient means than hitherto. This situation, in view of the fact that Berlin was by no means destroyed, meant that the Germans had already won the Battle of Berlin.")
But look at the data.
The main Battle comprised just 14 raids by Bomber Command, 7,403 sorties for the loss of 384 aircraft (5.2%). This is right on the figure that was considered unsustainable over a three month period, but hardly represents a defeat for the command.
Losses for the period 18/19 November to 31st march are a heavy but sustainable 3.8%.
It was always optimistic (actually impossible) to imagine that even 7,000 sorties could devastate a city the size of Berlin. During the Battle Bomber Command suffered a deterioration in efficiency, brought about by many factors, adverse weather, the long routes employed which meant fuel had to be carried at the expense of bombs, a greater reliance on inexperienced crews as casualties mounted, dilution of effort as up to 20% of the available force was used on diversionary raids. No.3 Groups Stirlings had been suspended from operations against Germany and 10 squadrons of Halifax IIs and Vs had also been withdrawn. This represented a loss of front line strength of 250 aircraft, about 30%!
There were also technical problems, most targets were outside the range of Oboe, arguably the most important factor, and H2S was just being fitted to PFF aircraft, and would prove something of a disappointment. Add to this evolving German tactics, particularly the night fighter force, and Berlin was always a tough prospect.
The Official History concluded.
"Despite the courage, vigour, resolve and endeavour which have made the Battle of Berlin famous in the annals of Bomber Command, a greater deployment of strength achieved results which were less effective than those which, at the cost of lower casualty rates, had followed the Battle of the Ruhr and particularly the Battle of Hamburg. This was due primarily to the operational limitations which continued to beset the force at long range and to the increasing effectiveness of the German air defences and especially the night fighter force. Though Berlin had felt the weight of war, the consequences were less severe than Sir Arthur Harris had hoped. From this point, however, Bomber Command went forward, but in alliance with other forces in the air an on the ground, to increasing, and presently decisive, success."
And that's the point. It was to some extent a self inflicted set back, just like the early USAAF deep penetration raids. These were not defeats in a decisive sense, both forces were able to recover and ultimately make significant contributions to the defeat of Germany.
Cheers
Steve