This August 14, 1944 letter from John McCloy, the U.S. Assistant War Secretary, says that a study was done about whether it was necessary to bomb Birkenau. Although the study disappeared after 1944, it must have concluded no mass murders were occurring and recommended against bombing because bombing was not ordered by U.S. President Roosevelt, the War Department, or the military.

                                     14 August 1944
Dear Mr. Kuboeitski: 			

I refer to your letter of August 9, in which you request consideration of a 
proposal made by Mr. Ernest Frischer that certain installations and railroad 
centers be bombed.

The War Department has been approached by the War Refugee Board, which raised the 
question of the practicality of this suggestion. After a study it became apparent 
that such an operation could be executed only by the diversion of considerable air 
support essential to the success of our forces now engaged in decisive operations 
elsewhere, and would, in any case, be of such doubtful efficasy that it would not 
warrent the use of our resources. There has been considerable opinion to the affect 
that such an effort, even if practicable, might provoke even more vindictive action 
by the Germans.

The War Department fully appreciates the humanitarian motives which prompted the 
suggested operation, but for the reasons stated above it has been felt that it can 
or should not be undertaken, at least at this time.

						Sincerely 
						John J. McCloy (Signed)
						JOHN  J.  McCLOY
						Assistant Secretary of War

This August 2, 1944 letter by Chief Air Marshall Norman Bottomley asks that a study be quickly conducted about whether it was necessary to bomb Birkenau. The study disappeared after 1944, but it must have determined no mass murders were occurring at Birkenau and recommended against bombing because bombing was not ordered by Prime Minister Churchill, Bomber Command, or the military.

TOP  SECRET 
Secretary of State Polder

A. C. A. S. (I) 
  		Copy to:  Y. C. A. S. 
			  P.S. to S. of S. 

Reference minute 1 at noq. I have discussed this subject with General Spaatz, who is 
quite sympathetic. 

1. Before we can consider any action, however, it is necessary to know more about 
the precise location, extent, and nature of the camps and installations at Birkenau. 
It is particularly necessary to have some photographic cover. 

2. Will you please have this produced as early as possible, so that the operational 
possibilities of taking some effective action from the air can be studied by the 
operational Commands and the Deputy Supreme Commander. I need not emphasize the need 
for absolute secrecy in this investigation. 

					M. H.  Norman Bottomley (signed) 
						\  D. C. A. S. 
2nd August 1944