the teachings of business school strategists.
This has to do with the concept of sunk costs: once you've spent a dollar, (or life), an additional dollar (or life) will not get the spent dollar (or life) back. In this case, the decision maker must focus on future costs, not past costs. So the concept of "we don't want to cut and run because that would mean our boys died in vain" is spurious at best, disingenuous certainly, and absolutely no reason to stay.
http://skepdic.com/sunkcost.html"When one makes a hopeless investment, one sometimes reasons: I can’t stop now, otherwise what I’ve invested so far will be lost. This is true, of course, but irrelevant to whether one should continue to invest in the project. Everything one has invested is lost regardless. If there is no hope for success in the future from the investment, then the fact that one has already lost a bundle should lead one to the conclusion that the rational thing to do is to withdraw from the project.
To continue to invest in a hopeless project is irrational. Such behavior may be a pathetic attempt to delay having to face the consequences of one's poor judgment. The irrationality is a way to save face, to appear to be knowledgeable, when in fact one is acting like an idiot. For example, it is now known that Lyndon Johnson kept committing thousands and thousands of U.S. soldiers to Vietnam after he had determined that the cause was hopeless and that the U.S. could never defeat the Viet Cong."