In the long shadow of that defeat, it became easy to forget that the now defunct Republic of Vietnam was holding its own, thanks to American air and logistical support, until Congress pulled the props out from under the Vietnamese. The same impulse can be seen in today's demands that American troops be withdrawn from Iraq, or at least not reinforced.

To quote General Petraeus' manual again, our enemy will "try to exhaust U.S. national will, aiming to win by undermining and outlasting public support."

A number of resolutions withdrawing support from the war are being readied in Congress, with Senators Carl Levin and Joe Biden leading the push to oppose the new strategy and the additional troops it requires. Hillary Clinton and Barack Obama will be right behind them, with an eye on next year's presidential election.

Vermont's Patrick Leahy would simply cut off funds for the troops. And he knows what effect that would have, for he cites the outcome in Vietnam as the example to follow: "This is the only way we stopped Vietnam when we finally had a vote in April 1975, a key vote on the power of the purse, that's what stopped it." And sealed freedom's fate in Vietnam. Not to mention Laos and the killing fields of Cambodia.

Unless the home front stands united, no new general in Iraq, even one with a new strategy that has begun to produce results, will be able to stave off defeat. And with defeat would come disastrous consequences throughout that volatile part of the world - and beyond.

Divided we fall.