Another job that Smeed gave me was to invent ways to estimate the effectiveness of various countermeasures, using all the evidence from a heterogeneous collection of operations. The first countermeasure that I worked on was MONICA. MONICA was a tail-mounted warning radar that emitted a high-pitched squeal over the intercom when a bomber had another aircraft close behind it. The squeals came more rapidly as the distance measured by the radar became shorter. The crews disliked MONICA because it was too sensitive and raised many false alarms. They usually switched it off so that they could talk to each other without interruption. My job was to see from the results of many operations whether MONICA actually saved lives. I had to compare the loss rates of bombers with and without MONICA. This was difficult because MONICA was distributed unevenly among the squadrons. It was given preferentially to Halifaxes (one of the two main types of British heavy bomber), which usually had higher loss rates, and less often to Lancaster bombers, which usually had lower loss rates. In addition, Halifaxes were sent preferentially on less dangerous operations and Lancasters on more dangerous operations. To use all the evidence from Halifax and Lancaster losses on a variety of operations, I invented a method that was later reinvented by epidemiologists and given the name “meta-analysis.” Assembling the evidence from many operations to judge the effectiveness of MONICA was just like assembling the evidence from many clinical trials to judge the effectiveness of a drug.
My method of meta-analysis was the following: First, I subdivided the data by operation and by type of aircraft. For example, one subdivision would be Halifaxes on Bremen on March 5; another would be Lancasters on Berlin on December 2. In each subdivision I tabulated the number of aircraft with and without MONICA and the number lost with and without MONICA. I also tabulated the number of MONICA aircraft expected to be lost if the warning system had no effect, and the statistical variance of that number. So I had two quantities for each subdivision: observed-minus-expected losses of MONICA aircraft, and the variance of this difference. I assumed that the distributions of losses in the various subdivisions were uncorrelated. Thus, I could simply add up the two quantities, observed-minus-expected losses and variance, over all the subdivisions. The result was a total observed-minus-expected losses and variance for all the MONICA aircraft, unbiased by the different fractions of MONICA aircraft in the various subdivisions. This was a sensitive test of effectiveness, making use of all the available information. If the total of observed-minus-expected losses was significantly negative, it meant that MONICA was effective. But instead, the total was slightly positive and less than the square root of the total variance. MONICA was statistically worthless. The crews had been right when they decided to switch it off.
I later applied the same method of analysis to the question of whether experience helped crews to survive. Bomber Command told the crews that their chances of survival would increase with experience, and the crews believed it. They were told, After you have got through the first few operations, things will get better. This idea was important for morale at a time when the fraction of crews surviving to the end of a 30-operation tour was only about 25 percent. I subdivided the experienced and inexperienced crews on each operation and did the analysis, and again, the result was clear. Experience did not reduce loss rates. The cause of losses, whatever it was, killed novice and expert crews impartially. This result contradicted the official dogma, and the Command never accepted it. I blame the ORS, and I blame myself in particular, for not taking this result seriously enough. The evidence showed that the main cause of losses was an attack that gave experienced crews no chance either to escape or to defend themselves. If we had taken the evidence more seriously, we might have discovered Schräge Musik in time to respond with effective countermeasures.
Smeed and I agreed that Bomber Command could substantially reduce losses by ripping out two gun turrets, with all their associated hardware, from each bomber and reducing each crew from seven to five. The gun turrets were costly in aerodynamic drag as well as in weight. The turretless bombers would have flown 50 miles an hour faster and would have spent much less time over Germany. The evidence that experience did not reduce losses confirmed our opinion that the turrets were useless. The turrets did not save bombers, because the gunners rarely saw the fighters that killed them. But our proposal to rip out the turrets went against the official mythology of the gallant gunners defending their crewmates. Dickins never had the courage to push the issue seriously in his conversations with Harris. If he had, Harris might even have listened, and thousands of crewmen might have been saved.
The part of his job that Smeed enjoyed most was interviewing evaders. Evaders were crew members who had survived being shot down over German-occupied countries and made their way back to England. About 1 percent of all those shot down came back. Each week, Smeed would go to London and interview one or two of them. Sometimes he would take me along. We were not supposed to ask them questions about how they got back, but they would sometimes tell us amazing stories anyway. We were supposed to ask them questions about how they were shot down. But they had very little information to give us about that. Most of them said they never saw a fighter and had no warning of an attack. There was just a sudden burst of cannon fire, and the aircraft fell apart around them. Again, we missed an essential clue that might have led us to Schräge Musik.
On November 18, 1943, Sir Arthur Harris started the Battle of Berlin. This was his last chance to prove the proposition that strategic bombing could win wars. He announced that the Battle of Berlin would knock Germany out of the War. In November 1943, Harris’s bomber force was finally ready to do what it was designed to do: smash Hitler’s empire by demolishing Berlin. The Battle of Berlin started with a success, like the first attack on Hamburg on July 24. We attacked Berlin with 444 bombers, and only 9 were lost. Our losses were small, not because of WINDOW, but because of clever tactics. Two bomber forces were out that night, one going to Berlin and one to Mannheim. The German controllers were confused and sent most of the fighters to Mannheim.