The ghosts of the Vietnam War no doubt hovered over a recently assembled conclave of President Donald Trump’s advisers as they deliberated over the deteriorating situation in Afghanistan.

In the Vietnam era, as today, the United States found itself engulfed in a seemingly never-ending war with mounting costs, unclear goals and few signs of success. In both Vietnam and Afghanistan, successive presidents faced much the same options: Withdraw, decisively escalate or do just enough to avoid losing. Like his predecessors in both wars, Trump chose the middle path – incremental escalation with no clear exit plan. Although Trump called it a “plan for victory,” Secretary of State Rex Tillerson candidly admitted that the additional American troops will likely do little more than “stabilize the situation.”

How can we to explain the seeming preference of U.S. presidents for muddling through – whether in Afghanistan or, 50 years ago, in Vietnam? This has been a central question in a course on the Vietnam War that I have offered for the past 30 years. In it, we look for answers in a fascinating debate among former officials that emerged in the late stages of the war.

Down a slippery slope

Harvard historian Arthur Schlesinger offered one point of view in his 1967 book “The Bitter Harvest.” A onetime adviser to John F. Kennedy, Schlesinger compared Vietnam to a quagmire: The first step into a quagmire inexorably draws one down a slippery slope. Schlesinger argued that officials in the Kennedy and Johnson administrations stumbled blindly into Vietnam without understanding where the U.S. commitment would lead. Escalation proceeded through a series of small steps, none of which seemed terribly consequential. Each succeeding step was taken in the optimistic belief that a little more effort – a bit more aid, a few more troops, a slight intensification of the bombing – would turn things around by signaling American resolve to stay the course. Faced with this prospect, the reasoning went, the North Vietnamese communists would sue for peace on American terms.

These flawed expectations, Schlesinger argued, arose from a decision-making system characterized by “ignorance, misjudgment and muddle.” A dysfunctional bureaucracy fed presidents misleading and overly rosy intelligence. The Vietnam War debacle, in other words, arose from inadvertence and folly.

Just don’t lose

In separate pieces, this interpretation of what went wrong was challenged by Daniel Ellsberg and Leslie Gelb. Both Gelb and Ellsberg had formerly served as Defense Department officials during the 1960s, and both helped to compile the famous “Pentagon Papers.”

Gelb and Ellsberg reached similar conclusions about the sources of U.S. policy toward Vietnam. Ellsberg argued that policymakers during the Kennedy and early Johnson administrations followed two rules:

1. Do not lose South Vietnam to communism, and
2. Do not involve the U.S. in a large-scale ground war in Asia.

Each rule drew upon recent precedent. The “loss” of China to communism in 1949 led to charges that Democrats were “soft on communism” and a wave of McCarthyite hysteria at home. On the other hand, the public would also not tolerate another ground war similar to the unpopular Korean engagement.

The perceived domestic political costs of either extreme – withdrawal or unrestrained escalation – steered Kennedy and Johnson toward the middle. As long as feasible, each president did enough to avoid losing South Vietnam but shunned the direct commitment of U.S. troops that military advisers insisted would be necessary to bring victory.

By 1965, the deteriorating political and military situation in South Vietnam cut this middle ground from beneath Johnson’s feet. The minimum necessary to stave off defeat now required the commitment of American combat troops. Even once this line had been crossed, however, troops were introduced in a gradual manner and Johnson balked at imposing higher taxes to pay for the war.

As Kennedy and Johnson anticipated, public support for the war waned as U.S. casualties mounted. Richard Nixon responded to these domestic pressures by undertaking “Vietnamization,” which gradually reduced American troop levels even while prolonging U.S. efforts to stave off a communist victory.

Ellsberg refers to this as a “stalemate machine.” Policymakers acted in a calculated manner to avoid losing for as long as possible, but understood that their policies could not bring victory. Stalemate was a conscious choice rather than a product of overoptimism or miscalculation.

While echoing Ellsberg’s account of the domestic constraints on U.S. policy, Gelb added two sets of international constraints. Withdrawal was ruled out because policymakers believed in the domino theory, which predicted that the loss of South Vietnam would set off a cascade of communist victories throughout Southeast Asia. They also feared that the U.S. would lose credibility with its allies if we failed to put up a fight in South Vietnam. For these reasons, as well as fears of a right-wing backlash, Kennedy and Johnson were unwilling to walk away from Vietnam.

Yet Kennedy and Johnson also feared the international risks of major escalation, Gelb argued. An invasion of North Vietnam raised the possibility that either China or the Soviet Union would intervene more directly or retaliate against U.S. interests elsewhere in the world. In an age of nuclear weapons, the U.S. preferred to keep the Vietnam conflict limited and to minimize the risks of superpower war.

From Vietnam to Afghanistan

Gelb and Ellsberg rejected Schlesinger’s argument that policymakers were overly optimistic and lacking in foresight. Rather, they saw policymakers as generally pessimistic, recognizing that the next step along the ladder of escalation would not be sufficient and that future steps would be necessary just to maintain a stalemate. With victory viewed as infeasible, presidents chose stalemate as the least bad among a set of terrible options. Presidents had no clear exit strategy, other than the hope that the enemy would weary of the conflict or that the problem could be passed along to the next president.

Instead of blaming bureaucratic bumbling, Gelb argues that “the system worked.” The bureaucrats did exactly what top policymakers asked them to do: Avoid losing Vietnam for more than a decade. The problem lay rather in the underlying assumption – never questioned - that Vietnam was a vital interest of the United States.

Who was right?

I’d contend that Gelb and Ellsberg make a more convincing case than Schlesinger. Muddling through offered presidents a politically safer short-run alternative to withdrawal or major escalation.

A similar dynamic appears at work in the U.S. approach to Afghanistan, where Presidents Bush, Obama and Trump have each accepted stalemate over the riskier options of retreat or decisive escalation. Against an entrenched Taliban insurgency, U.S. policy has been driven by the need to stave off the collapse of weak local partners rather than the pursuit or expectation of military victory. Even President Barack Obama’s surge in Afghanistan provided fewer than half the troops requested by the military. On the other hand, Obama later retreated from his own stated deadline for total withdrawal, opting to leave 11,000 troops in place. Now Trump has also reneged from previous pledges to disengage from Afghanistan, instead sending additional troops.

It may be that the logic of the stalemate machine is built into the very concept of limited war. Or that it is a predictable consequence of how presidents manage the constraints posed by American politics. In any case, the histories of U.S. military involvements in Vietnam and Afghanistan should serve as warnings to future presidents who might be tempted to again jump onto the treadmill of perpetual war.

David Skidmore does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.