Many observers, both past and present, have predicted that the downfall of corrupt, authoritarian regimes allied to the United States would lead to their replacement by more fearsome authoritarian regimes. These replacement regimes have been and will be hostile toward the United States, far more oppressive toward their people, and more threatening toward their immediate neighbors than the regimes they overthrew. The replacement of pro-American authoritarian regimes by anti-American ones in China in 1949, in Indochina in 1975, in and Iran in 1979 are just a few of many such instances. If the U.S. withdrawal from Afghanistan leads to the downfall of the Kabul government and the return of a Taliban regime, then this trend will surely continue. 

But there is something else that often—even if not always—happens after a regime allied to the United States is replaced by a regime that is hostile toward it: serious conflict takes place between America’s adversaries. This has occurred on numerous occasions.  

The coming to power of the People’s Republic of China in 1949 was soon followed by the onset of the Sino-Soviet rift that became overt by 1960 and lasted until the end of the Cold War.  Fighting along their common border in 1969 threatened to turn into a wider war between China and Russia.  

In Ethiopia, the 1974 overthrow of America’s ally, Emperor Haile Selassie, who was replaced by a Marxist-Leninist regime, was followed by a war between the new Marxist regime in Ethiopia and the pro-Soviet regime in next-door Somalia in 1977–78.  Moscow failed in its efforts to mediate between its two Marxist allies and Somalia defected from the Soviet camp to the Western one.  

After the U.S. withdrawal from Indochina in 1973 and the Marxist takeovers in South Vietnam, Cambodia, and Laos in 1975, pro-Moscow Vietnam invaded pro-Beijing Cambodia in 1978 and China and Vietnam fought a brief war along their common border in 1979.  A common concern about China helped bring about the improvement in Washington’s relations with Hanoi, which began under President Bill Clinton and has continued ever since.  

In Iran, the downfall of the pro-American Shah and the rise of the anti-American Islamic Republic in 1979 was soon followed by the 1980–88 war between Iran and Saddam Hussein-ruled Iraq. Despite the common antipathy the countries had for America and the West, Iran remained neutral when a U.S.-led coalition ousted Iraqi forces from Kuwait in 1991. The anti-American regimes in Tehran and Baghdad continued to keep each other in check until 2003 when a U.S.-led coalition overthrew Hussein and opened Iraq up to the spread of Iranian influence. 

After the United States withdrew its forces from Iraq in 2011, the Arab Shia-dominated Baghdad government with close ties to Tehran, which America left behind, faced an existential threat from the Sunni jihadist Islamic State movement beginning in 2014. The movement was not only anti-Western but anti-Shia and anti-Iranian. Iran may have had to undertake much greater efforts to protect its Arab Shia allies as well as its influence in Iraq if the U.S. re-intervention in Iraq against the Islamic States had not relieved Iran of such a burden. Similarly, U.S. military action against the Islamic State in Syria relieved both Russian and Iranian forces of the need to directly combat Islamic State forces.  

In that the downfall of governments allied to the U.S. has been followed so often in the past by conflict between U.S. adversaries, the question that arises is whether this will happen again—especially in Afghanistan. There is, of course, no guarantee that it will. But even though the Taliban have not yet ousted the U.S.-backed Kabul government, anti-American regimes in Russia, China, and Iran are already exhibiting nervousness about how the Taliban’s possible return to power might negatively affect them. China does not want the Taliban to support the Muslim Uighur opposition in neighboring Xinjiang, Russia does not want it to undermine Moscow’s secular allies in Central Asia, and Iran does not want to see it support Sunni opposition to the Shia clerical regime in Tehran.  Even though the Taliban has not yet come to power, it has already been fighting against Islamic State forces in Afghanistan. Finally, while Pakistan has long supported the Taliban (and should be considered an adversary of the United States to the extent that it has done so), there is also the possibility that a restored Taliban regime could pose problems for Pakistan. After all, the Taliban have reportedly already begun talks with Pakistan’s arch-rival, India.  There appear to be several opportunities for the pattern of U.S. adversaries turning on each other to emerge in Afghanistan if the Kabul government falls and the Taliban returns to power. 

The current U.S. drawdown of its forces from Iraq does not seem likely to lead to Iranian efforts to undermine the Baghdad government since U.S. actions in Iraq up to now have already allowed Iran to gain so much influence over it.  There are signs, though, that many Iraqi Shias are now at odds with Iran over the role it plays in Iraqi politics.  In addition, the impending end of combat operations by U.S. forces, which were sent back to Iraq to fight the Islamic State, may contribute to the latter’s resurgence and to a conflict between the Islamic State and the Baghdad government as well as a conflict between the Iraqi Arab Shia militias and Iran. In other words, there appear to be opportunities for the pattern of U.S. adversaries turning on each other in Iraq too.  

Because this pattern has occurred so often in the past, it seems highly likely that it will occur again. This is not to say that the United States should be unconcerned about the downfall of allied governments and the possibility that they will be replaced with hostile ones since U.S. adversaries are likely to develop conflictual relations with each other anyway. But the U.S. government should be prepared for this scenario arising and seek to take advantage of it when it does occur.   

Sometimes, U.S. adversaries who have turned against each other will raise the possibility of Washington working with a former adversary as an ally against a more formidable common foe. This is something the United States did with Vietnam vis-a-vis China. Sometimes, though, the best course of action may be to simply do nothing while U.S. adversaries that remain hostile toward America and the West expend their venom on each other. Above all, the United States should be wary of how its intervention against one adversary can unintentionally benefit another one. For example, the U.S. intervention against the Islamic State in Iraq ended up serving Iranian interests. 

The downfall of the Kabul government and the return to power of the Taliban, should this occur, will be something terribly painful for the people of Afghanistan. It will also mark the failure of a two-decade-long U.S. effort to build up an Afghan government that would prove more capable and attractive than the Taliban. But while there will be many who engage in recriminations over what went wrong and whether a better outcome could have been achieved, Washington will have to deal with the situation that emerges no matter how undesirable it is. The likelihood that conflict will develop between the Taliban and other U.S. adversaries may present opportunities that the United States can take advantage of. But it can only do so if it recognizes both the opportunities and the dangers of navigating conflicts between U.S. adversaries.  

Mark N. Katz is a professor of government and politics at the George Mason University Schar School of Policy and Government, and a nonresident senior fellow at the Atlantic Council.  

 Image: Reuters