America’s second gift to Iranian security was the 2003 invasion of Iraq. Saddam was Iran’s mortal adversary. Iran fought a brutal war against Iraq in the 1980s, suffered hundreds of thousands of casualties, and endured chemical-weapons attacks and missile strikes on Iranian cities. After 2003, with Saddam deposed, Iraq was transformed into a virtual client state of Iran. Tehran is now the indispensable nation in Iraqi politics, deciding government policy and settling disputes. When the Iraqi Kurds pursued an independence referendum in 2017 that threatened full-scale conflict with Baghdad, it was Iran, not the United States, that negotiated an end to the standoff.

If Iran had tried to overthrow Saddam Hussein directly through an invasion, it would have provoked a balancing response from Arab states and the West. Instead, American planes descended from the sky like blessed angels to hammer Saddam’s regime with “shock and awe,” while Tehran reaped the rewards.

Still, the United States wasn’t done helping Iran. In 2014, after ISIS swept into northern Iraq, the United States constructed a coalition of over 80 states to battle the Sunni extremists. Who benefited? Iran, of course. As ISIS’s power waned in Syria and Iraq, Iran entrenched its strategic position. For example, Iran trained Shia militias to fight ISIS, known as Popular Mobilization Units, creating a powerful military asset.

In summary, the United States has a consistent tendency to aid its supposed nemesis. For two decades, the United States poured treasure into the Middle East and Iran cashed the checks. Washington removed enemies on Iran’s eastern and then western borders. Tehran’s forces can now cross a “land bridge” from Tehran to Beirut, which Washington helped to build.

The explanation for American generosity is that Washington pursued a short-term strategy to remove bad guys and ignored the broader political consequences. Time and again, battlefield success created a power vacuum—into which Iran eagerly stepped.

The exception, where Washington successfully checked Iranian ambitions, was not through the use of force but through diplomacy: the Iran nuclear deal. A combination of tough sanctions and hard-nosed multilateral negotiations led Iran to shut down all pathways to a nuclear bomb for a decade or more, place two-thirds of its centrifuges in storage, give up around 95 percent of its uranium stockpile, and accept the most intrusive inspections regime in modern history.

By ripping up the nuclear deal, Trump has returned to an old and failed American strategy: Disregard the political ripple effects, apparently fail to think multiple moves ahead, and potentially further Iranian interests. Britain’s Foreign Secretary Boris Johnson wrote in The New York Times, “Only Iran would gain from abandoning the restrictions on its nuclear program.”