As always, Mark Steyn is the last word:

Demonstrating the will to lose as clearly as America did in Vietnam wasn’t such a smart move, but since the media can’t seem to get beyond this ancient jungle war it may be worth underlining the principal difference: Osama is not Ho Chi Minh, and al-Qa’eda are not the Viet Cong. If you exit, they’ll follow. And Americans will die – in foreign embassies, barracks, warships, as they did through the Nineties, and eventually on the streets of US cities, too.