SAN FRANCISCO

PARALLELS BETWEEN the war in Iraq and the war in Vietnam practically draw themselves. Many have long since noted the most obvious similarities: In each conflict, the United States struggled to defeat an unconventional enemy, using unconventional tactics, in an unforgiving environment.

Recently, President Bush drew his own parallel: “Then as now, people argued the real problem was America’s presence and that if we would just withdraw, the killing would end.” Of course, any comparison between the wars in Vietnam and Iraq is bound to be nearly as controversial as the conflicts themselves. But beyond the hyperbole, relevant comparisons are there to be made. And as the momentum to exit Iraq gathers steam, the lessons from Vietnam can be particularly illuminating.

During the U.S. war in Vietnam, roughly from 1965 to 1973, troop levels varied greatly, climbing to a peak of over 500,000 in early 1969. The withdrawal of combat troops, however, actually began in earnest that very same year, as President Nixon tried to implement his “Vietnamization” policy of shifting the burden of the fight to the South Vietnamese. Troop levels dropped gradually over the coming years, as South Vietnam shouldered a greater combat burden and as negotiations with North Vietnam progressed in fits and starts. Withdrawal of combat troops from Vietnam was completed in 1972 (although “advisers” remained behind), and the Paris Peace Accords — which formally ended U.S. involvement in the Vietnam War — were signed in early 1973. From the U.S. perspective, these accords provided an expedient cover for the military withdrawal, or a “peace with honor,” as Nixon described it. Of course, neither the United States nor its South Vietnamese allies saw much of either. The Paris accords ultimately fell apart, and South Vietnam fell to the North in 1975.

By contrast, U.S. troop levels in Iraq have remained fairly consistent through the war — 100,000-200,000 since the invasion, in 2003. This has remained true both through Bush’s own strategy of “Vietnamization” (when the emphasis was on training Iraqis to assume security responsibilities from the United States) as well as his latest “surge” strategy (emphasizing the security of Baghdad with U.S. troops).

Moving forward, the comparison with Vietnam falls apart even more. The various Iraqi resistance groups lack a formal state sponsor with which the U.S. could negotiate a withdrawal; despite its clear influence, Iran cannot play the role of North Vietnam today. A regional diplomatic dialogue may emerge alongside the withdrawal process, and the U.S. will surely try to coordinate its departure with the Iraqi government. But the eventual U.S. withdrawal will probably not be accompanied by the same kind of political or diplomatic cover that the Paris Accords offered in Vietnam. As unsuccessful as the Paris Accords were, though, it isn’t clear that such cover is really that valuable.

Despite these differences, one important lesson can be gleaned: Withdrawal does not occur for withdrawal’s sake alone. The U.S. departure from Vietnam did not occur in isolation, and the eventual U.S. withdrawal from Iraq won’t, either. In each case, the military departure will be part of a broader political and military strategy with goals beyond the simple extrication of U.S. forces. Given its global standing, the United States does not have the luxury of simply leaving devastated, chaotic countries in its military’s wake. Rather, any military withdrawal from Iraq will be but one component of a broader strategy designed to ensure stability and security in that country. This is not to say that such a strategy will be successful; it certainly wasn’t so in Vietnam, and the prospects are dim for anything better in Iraq. But it does suggest that the withdrawal from Iraq will not be quick, and it will not be easy. This is a reality that will confront Democrats and Republicans alike.

Another interesting parallel between Vietnam and Iraq does present itself. Throughout the prolonged, gradual withdrawal from Vietnam, the United States continued to suffer casualties. It also remained very engaged in combat operations, specifically in the form of the aerial bombardment of North Vietnam. From the perspective of many on both sides of the conflict, then, the U.S. withdrawal process was somewhat illusory — the troops may have been leaving, but the war was still on. The same will probably be true in Iraq. The United States has invested so much in its military infrastructure in Iraq that a complete, 100 percent withdrawal remains unlikely for the foreseeable future. And even as the troops begin to leave, their air cover will remain in place, based from carriers in the Persian Gulf and from other bases throughout the region.

Compared with Vietnam, the bombers over Iraq may be faster and their bombs smarter. But as in Southeast Asia, it’s unlikely that the Iraq war will end when the last U.S. soldier leaves the battlefield.

Daniel Widome, an occasional contributor, is a San Francisco-based writer and foreign-policy analyst ( Daniel.Widome@gmail.com).