2019’s drumbeat of American-Iranian tensions became a crescendo in the first days of 2020. The year began with the assassination via U.S. airstrike of senior Iranian general Qassem Soleimani and Iran’s retaliation with ballistic missiles against American bases in Iraq. Each side has escalated in an attempt to make the other back down—and neither side has done so. Now the United States faces a choice—keep the cycle of escalation going or break free. Choosing the former could have lasting and negative strategic consequences.

Iranian officials from the Supreme Leader on down have vowed revenge and the country’s intelligence minister has branded the assassination “an act of war” against both Iraq and Iran. Yet the use of Iranian forces who fired their missiles from Iran, and Iran’s subsequent claiming of the attack, are surprising. Iran cannot win a war with the United States and would suffer greatly were it to try. Its strategy has been to wait out the Trump administration while raising the costs of the maximum pressure campaign. A war would be a major shift in that strategy, possibly with the aim of making Trump lose in 2020.

Yet three factors make that a hard road: wars can often strengthen hawkish candidates in the short term; the costs to Iran’s regime could be extreme; and many Iranian retaliatory options would poison public opinion, making diplomacy very hard for a Trump successor. Further, many figures in Iran see both parties as unfriendly. There has been much talk about how Americans only understand force—which eerily parallels remarks from a senior State Department official after the Soleimani killing. The State official also said that “timidity will invite more aggression,” and there has been a stream of threats against Iranian retaliation. Each side seems to have been proven wrong in its assumption that more force will deescalate the situation—but it is not clear that either has realized that.

Leaving the Soleimani attack unanswered would have been humiliating for Iran. Tehran did accept such a humiliation in the past, after a 2008 CIA-Mossad operation killed Imad Mughniyah, an infamous Hezbollah operative. Yet it helped that nobody had claimed responsibility for that attack for many years. Israel has largely been quiet, too, about its many airstrikes in Syria and Iraq against Iran-aligned targets. In contrast, the United States has trumpeted its role in killing Soleimani, making it harder for Iran to not hit back. The Soleimani strike was an all-in bet that America’s superior power would force Iran to back down. We bet wrong.

If the confrontation continues to spiral, Iran will enjoy significant flexibility in its responses. It has cultivated proxy forces, sleeper agents, those missiles, and more. It can conduct attacks that are obviously an Iranian action, or hard to attribute. It can strike close to Iran, or in faraway places like Argentina, Georgia, India, Thailand, Kenya, or Europe. It can use Iranian forces or third parties—see the Kitaib Hezbollah rocket attacks that kicked off this crisis. It can harass the United States or U.S. allies—Saudi Arabia may be as prime a target as it was in September. Attacks can be big or small. They can aim at degrading key abilities, striking important symbols, or highlighting weaknesses. Iran is likely to choose several options across this spectrum, hoping to hit back without provoking a broader war. Yet such actions are shaped by the logic of war, which, as the great Clausewitz tells us, runs not only on reason but on chance and emotion. Each tit-for-tat response contains the seeds of miscalculation and further escalation.

Zooming out, mere ongoing confrontation will have a serious impact on U.S. strategy. The greater danger of an Iranian attack has led to thousands more troops being sent to the region. If a wider war breaks out, there will be many more. This spells trouble for America’s ostensible reorientation towards “long-term, strategic competition” with great powers like Russia and China, announced in the 2018 National Defense Strategy and foreshadowed by the Obama administration’s “Pivot to Asia” and even the pre-9/11 Bush administration. The unpopular endless wars of the Middle East are getting new life.

Even without a wider war, this may be the end of the U.S. military presence in Iraq. Killing Soleimani on Iraqi soil against Iraq’s wishes was, in the words of Iraq’s prime minister, “a massive breach of [Iraqi] sovereignty.” American forces there were already a contentious issue. Abu Mahdi al-Muhandis, who was killed alongside Soleimani, was a major figure in both the Kitaib Hezbollah militia and the Popular Mobilization Forces—represented by a coalition in Iraq’s parliament. Prominent clerics Ali al-Sistani and Moqtada al-Sadr, neither of whom are in Iran’s pocket, condemned the attack, and Iraq’s parliament, in an emergency session on Saturday, pressed the Iraqi government to order American troops out. Without troops, the U.S. diplomatic and intelligence presence in Iraq may also be curtailed. This could ironically increase Iranian influence in Iraq.

Few will think of Russia and China during this moment, but they may be the greatest long-term beneficiaries of all these escalations, and their choices in the coming months will be critical. Neither wants a war, but both have cause for fury.

Soleimani had traveled to Moscow in 2015 ahead of the Russian intervention in Syria, where Iran and Russia had jostled in a testy alliance. China depends on oil from the Middle East. Russia and China tend to oppose U.S. interventions, especially when they are not allowed to sign off on them first, and each sees an expansive U.S. role in global security as a threat. The attack contributes to a trend in which U.S. actions give these two states reason to put aside their differences—something America had sought to avoid since the days of Nixon and Kissinger in Beijing. Each can use Iran to make things harder for America. For example, Russia chose not to sell advanced surface-to-air missiles to Iran during the arms embargo ahead of the nuclear deal. But Russia can go the other direction, providing Iran with military technologies that would make U.S. aggression more costly. (Russia has already allegedly offered a suite of advanced surface-to-air missiles to Iraq.) China, to a lesser extent, can do the same. This would detract further from U.S. attempts to focus more on Russia and China.

All this means there could be serious, negative, strategic consequences for the United States if this keeps going. The Islamic Republic has responded—now it is imperative that America not allow itself to be drawn into a war.

John Allen Gay is coauthor of War with Iran: Political, Military, and Economic Consequences (Rowman and Littlefield, 2013). He tweets @johnallengay.