The United States is edging closer to what may be the most fateful choice of its modern history: whether to take bolder and more aggressive action to defend a beleaguered people against the world’s other major nuclear power. As the brutal Russian invasion of Ukraine grinds on and the humanitarian toll rises, many observers have demanded just such action in increasingly urgent terms. Some of these appeals focus on proposed no-fly zones, some on the idea of shipping MiG-29s to Ukraine. Others represent more general demands for military threats against Russia, or efforts to create humanitarian corridors.

Many of these proposals have been posed in confrontational, even dismissive language, depicting doubters as appeasers and fools. One of the most respected American defense intellectuals, Eliot Cohen, recently mocked the “hand-wringing over escalation” and insisted that Russian President Vladimir Putin will back down if adequately menaced. “We are dealing with an enemy that is vicious but weak,” Cohen claimed, “menacing but deeply fearful, and that is likely to crack long before our side does — if only we have the stomach for doing what needs to be done.” Retired U.S. Air Force Lt. Gen. David Deptula portrayed a United States “frozen in its tracks, fearing Putin’s unpredictable wrath.” The journalist David Rothkopf tweeted that anyone proposing an “off-ramp for Putin” should be “ashamed” of themselves.

The moral urgency that drives such pleas is entirely understandable. Russia’s invasion is criminal, Ukraine’s resistance courageous, the humanitarian toll horrific, and U.S. support for that resistance more essential every day. Yet many demands for more belligerent actions reflect a mindset commonly associated with foreign policy catastrophes: acting based on an overwhelming sense of what a country must do, rather than a primary and rigorous assessment of which course of action would best advance its interests and goals. The pattern can be described as “imperative-driven judgment.” It is foreign policy by moralistic duty.

Appeals for bolder action in Ukraine will understandably only grow more intense as the appalling humanitarian toll mounts. But imperative-driven action almost always leads countries astray — and in the days and weeks ahead, it will be critical for the United States to stay alert for its symptoms.

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History offers a litany of such cases, when imperative-driven thinking caused leaders to brush aside issues of risk and feasibility, quash dissent, and embrace disaster. Apart from Iraq, modern U.S. foreign policy offers at least two potent examples: the Bay of Pigs and Vietnam.

Confronting the Castro regime in Cuba after the revolution of 1959, the degree of urgency and wrath propelling the U.S. effort grew into a sort of moral obligation. Plans to drive Castro from power became an imperative. On the way to the Bay of Pigs, U.S. officials reached the point — as Jim Rasenberger explains in his compelling account The Brilliant Disaster — at which they were “operating under conditions that made the venture almost impossible to resist. At a time when Americans were nearly hysterical about the spread of communism, they simply could not abide Castro. He had to go.”

In Vietnam, Lyndon Johnson’s escalation decisions were couched in the language of obligation — the United States simply could not allow a communist victory. He repeated some version of the domino theory many times: “If they take South Vietnam, they take Thailand, they take Indonesia, they take Burma, they come right on back to the Philippines.” He worried about ruined credibility and the domestic political price for withdrawal and felt the clear imperative to stay. “Our national honor’s at stake,” he said in a June 1965 conversation with Sen. Richard Russell. That same month, speaking with Robert McNamara, Johnson concluded simply: “We can’t give up. I don’t see anything to do except give [the commanders] what they need, Bob. Do you?”