Overall 268,657 male and 131,560 female prisoners were registered in Auschwitz, 400,207 in total. Many prisoners were never registered and much evidence was destroyed by the SS in the final days of the war, making the number of victims hard to ascertain. Himmler visited the camp on 17 July 1942 and watched a gassing; a few days later, according to Höss's post-war memoir, Höss received an order from Himmler, via Adolf Eichmann's office and SS commander Paul Blobel, that "[a]ll mass graves were to be opened and the corpses burned. In addition the ashes were to be disposed of in such a way that it would be impossible at some future time to calculate the number of corpses burned."
Slovak rabbi Michael Dov Weissmandl was the first to suggest, in May 1944, that the Allies bomb the rails leading to Auschwitz. At one point British Prime Minister Winston Churchill ordered that such a plan be prepared, but he was told that precision bombing the camp to free the prisoners or disrupt the railway was not technically feasible.[not in citation given] In 1978, historian David Wyman published an essay in Commentary entitled "Why Auschwitz Was Never Bombed", arguing that the United States Army Air Forces had the capability to attack Auschwitz and should have done so; he expanded his arguments in his book The Abandonment of the Jews: America and the Holocaust 1941–1945 (1984). Wyman argued that, since the IG Farben plant at Auschwitz III had been bombed three times between August and December 1944 by the US Fifteenth Air Force in Italy, it would have been feasible for the other camps or railway lines to be bombed too. Bernard Wasserstein's Britain and the Jews of Europe (1979) and Martin Gilbert's Auschwitz and the Allies (1981) raised similar questions about British inaction. Since the 1990s, other historians have argued that Allied bombing accuracy was not sufficient for Wyman's proposed attack, and that counterfactual history is an inherently problematic endeavor.