One thing that irritates me about the 'leave no man behind' meme is that we have knowingly done so in the past. I have read quite a few books about the Cold War recon and espionage efforts. The USA had several recon planes shot down over or near the Soviet Union and the PRC. There have been eyewitness reports, some of questionable validity, of American airmen being held as prisoners in Soviet and PRC prison camps. Apparently, with the fall of the Soviet Union and the opening of the archives, we are reasonably certain that no live prisoners from this era are still around, but I would bet cash money that we knew at the time that captured American airmen were being held by the Soviets and PRC and we left them there.