On Feb. 1, the Trump administration announced its decision to withdraw from the Intermediate-Range Nuclear Forces (INF) Treaty. The following day, Russian President Vladimir Putin followed suit. This set off a six-month negotiation period during which the United States and Russia can attempt to resolve their differences before a full withdrawal, though such a resolution seems unlikely.

There may be strategic advantages to abandoning the INF agreement. Russia has certainly violated its terms over the past decade, and remaining party to a treaty in which one signatory violates terms may limit options for the other. And then there’s the issue of China: Not a signatory, China is free to develop weapons that the United States and Russia cannot. This is a security concern for the Americans and Russians alike.

Yet withdrawing will ultimately weaken security for the United States and its Western allies at a time when their alliances are already under strain. Given that strain, once the treaty is undone, it is likely to be undone for good, leaving few options to avoid the needless militarization that will surely follow.

That’s because the treaty, a response to the remilitarization of the late Cold War, relied on a united West. While the negotiations were conducted between the United States and Soviet Union, their ultimately successful outcome owed much to the unity of the Western alliance and the serious consultation on arms control that occurred within NATO.

Signed in 1987, the INF Treaty emerged from the controversy over the Soviets’ 1976 deployment of the SS-20 missile. This missile served two strategic goals for the U.S.S.R.: It expanded the Soviet arsenal and potentially weakened relationships between NATO states and, therefore, the alliance itself. That’s because, with its short range, the missile threatened only continental Europe. Moscow’s strategy initially worked: While European leaders wanted an immediate NATO response, U.S. policymakers shrugged off the threat. The alliance suffered as a result.

It took more than three years for NATO to overcome the discord. In 1979, the alliance issued a “dual-track” decision that responded to the Soviet missiles by planning to deploy American intermediate-range missiles in several European countries and offering arms control negotiations on this class of weapon. Predictably, the dual-track decision angered Soviet leaders, who initially refused to negotiate until NATO rescinded its intention to deploy. NATO proceeded anyway.

When the Soviet Union invaded Afghanistan two weeks later, East-West relations broke down, derailing ongoing arms-control efforts. Seeing a unified response to this aggression as essential, NATO leaders created a Special Consultative Group to facilitate discussion about possible INF controls.

This strategy worked. In July 1980, when the Soviets at last agreed to talks, consultation within NATO had already been established. With President Ronald Reagan’s election bringing more bellicose rhetoric, the Special Consultative Group proved essential in mediating opinion among the allied powers. And given rising anti-nuclear sentiment in Europe, the Europeans required a serious commitment to the arms-control half of the dual-track decision to retain the political will for deploying new weapons. Not only had European opinion convinced the United States of the importance of responding to the Soviet deployment in the first place, but as U.S. interest in arms control seemed to wane following the election, the Europeans also pressured the Americans to continue along the arms-control path.

And so arms control became a “joint enterprise,” in the words of a 1981 Special Consultative Group meeting. Even if opinions sometimes diverged, the United States worked with European policymakers to ensure that they presented a unified front during the negotiation process. Achieving this gave the Reagan administration international credibility. Indeed, the head of the U.S. negotiating team in Geneva, Paul Nitze, noted the importance of being “seen to be trying.” Reagan, for his part, noted that “this consultative process has already proven one of the most intensive and productive in the history of the North Atlantic alliance. ”

In November 1983, when the United States finally deployed the first round of INF in Europe, the Soviets walked out of the negotiations. They didn’t return to the negotiating table for years. The Soviets’ continuing deployments of SS-20s further helped NATO to maintain its position in Western public opinion. Consultation within NATO had helped the alliance to engineer political unity and solidarity, even helping member nations to marginalize internal dissenting opinions.

It was not until 1985 and the election of Mikhail Gorbachev as general secretary of the Communist Party that the Soviets began negotiations anew, leading to the almost-successful Reykjavik Summit in 1986 and, the following year, the INF Treaty itself. It took a crisis of leadership (Gorbachev was the third Soviet leader since Leonid Brezhnev’s death in 1982), tremendous economic problems and eventually radical reforms to bring the Soviet Union to the negotiating table.

The key? The Soviets negotiated from a position of weakness, while the United States had strengthened its hand through NATO collaboration over the preceding years.

The volume of work required to negotiate the treaty, as well as the participants’ relative positions, should give pause to anyone thinking about withdrawal today. Unified Western leadership enabled the United States to successfully counter the Soviets at Geneva. The Trump administration has worked to erode this unity throughout its tenure, from public criticism of NATO allies to an outright lack of consultation on several important issues.

Moreover, key leaders within NATO do not enjoy the relative strength of their predecessors. Trump faces the upcoming report from special counsel Robert S. Mueller III; British Prime Minister Theresa May clings to power as her country attempts to manage Brexit; and Angela Merkel has already announced her intention to step down as Germany’s chancellor, calling into question her nation’s future ability to lead in NATO. All of this speaks to larger divisions within the Western alliance — in particular, a rising tide of far-right politics and nativism that is openly hostile to the alliance politics of the late Cold War.

The Trump administration’s willingness to unilaterally abandon important arms control treaties, first with Iran and now with Russia, makes the world less safe. Understanding the work that went into negotiating them in the first place — and indeed, the important role that the increasingly weak Western alliance played — might well make those Trump supporters suffering from collective amnesia just slightly less cavalier about dismantling the bedrock treaties that reduced Cold War tension.