How to win a war

In the spring of 1968, the Vietnamese communists were on the run in the wake of the failed Tet Offensive. Gen. William C. Westmoreland, the U.S. commander in Vietnam, urgently requested a surge capability to exploit the allied victory, hammer the enemy troops and potentially end the war. But President Lyndon B. Johnson, harried by leadership challenges from within his own party and facing a recalcitrant Congress, failed to act decisively.

For weeks, Mr. Johnson dithered, commissioned studies, held meetings and sought advice. Meanwhile, a leaked report about the proposed troop buildup was spun as evidence of a U.S. defeat in Tet. The opportunity passed. Rather than lead, Mr. Johnson defaulted. Rather than push for victory, he asked the enemy for negotiations. Rather than rally the American people, he chose to throw in the towel and not run for re-election.

In January 2007, President George W. Bush faced a much more difficult challenge. The situation in Iraq had vastly deteriorated. Casualties were increasing. His public approval rating was 28 percent, according to a CBS News poll, and around two-thirds of Americans opposed the war. Mr. Bush also had to contend with a freshly elected Democratic Congress that claimed an antiwar mandate.

Mr. Bush knew he had one last chance to pull out a victory. He appointed Gen. David H. Petraeus, architect of the latest counterinsurgency doctrine, to command Multi-National Force - Iraq. Gen. Petraeus implemented the strategy that has become known as the "surge," which was a comprehensive shift in the conduct of the war. Gen. Petraeus requested and was given an additional 30,000 troops to promote stability while the strategy was implemented and to provide a bridge capability while Iraqi forces were trained to take over the fight.

Mr. Bush pushed the surge through dogged congressional resistance. In the end, the Democrats reluctantly gave the administration until September 2007 to show results, and sharpened their knives for the expected rout. It was not much time, but it turned out to be enough. Gen. Petraeus reported to Congress that conditions in Iraq had largely stabilized. Tragedy had been averted, and all the signs were pointing in the right direction. Eighteen months later, casualties had fallen 85 percent, the number of security incidents had dropped by about two-thirds, and the sense of crisis had passed.

Some things had not changed - Mr. Bush's approval ratings had not recovered, and the Democrats were still declaring the war a failure. But this successful strategy, which then-Sen. Barack Obama strongly opposed, is what allows President Obama to withdraw from Iraq without suffering the stigma or consequences of defeat.

Now Mr. Obama faces a pivotal moment. Conditions in Afghanistan continue to deteriorate. Gen. Stanley A. McChrystal, the commander of U.S. forces in Afghanistan, has assessed the situation and concluded that more troops are needed to prevent a defeat. Congress has signaled that it would resist a request for reinforcements.

Mr. Obama is in a much better position than Mr. Bush was. His approval ratings for handling the war are about 50 percent, his party has a complete lock on Congress, and the leadership does not want him to fail. The president introduced his new strategy in March, and Gen. McChrystal is widely regarded as the right man to implement it. The experience in Iraq stands as a model for success.

Mr. Obama has an opportunity to lead. He should stand by his strategy and fight to give his commander in the field the resources he needs to win. He should use his persuasive powers to bring together the members of his party to support him, joining the Republican leaders in a spirit of bipartisanship. It is not the time to abandon his strategy, redefine the mission or leave the troops in the field without the resources they need for victory.

It is time for the president to step up. Winning a war is never easy, but the consequences of losing one are even harder. Last March, Mr. Obama called his Afghan war strategy "stronger and smarter." It is time for him to justify those words with deeds.