Taking advantage of disputes between adversaries is an attractive idea and the United States has had success at this in the past. The most spectacular example was how Richard Nixon and Henry Kissinger were able to take advantage of the growing Sino-Soviet dispute to improve U.S. relations both with China and the Soviet Union in the early 1970s. But there have been other examples as well. 

In his 2021 book, The Power to Divide: Wedge Strategies in Great Power Competition, Timothy W. Crawford described how in 1940-41 the United States and the United Kingdom succeeded at dissuading Spanish leader Francisco Franco from allowing German forces into Spain and attempting to seize Gibraltar from Britain by providing food assistance to his civil war-ravaged country. In the late 1940s, the United States was able to take advantage of the growing dispute between two communist leaders—the Soviet Union’s Joseph Stalin and Yugoslavia’s Josip Tito—to help communist Yugoslavia exit the Soviet bloc and be neutral throughout the rest of the Cold War. In the early 1970s, Nixon and Kissinger were able to leverage Egyptian leader Anwar Sadat’s disillusionment with the Soviet Union to facilitate Egypt’s move from being a Soviet ally to an American one. In the mid-1980s, the previously hostile U.S.-Iraqi relationship underwent a dramatic improvement for a few years on the basis of common antipathy toward Iran. A second rapprochement between Washington and Moscow occurred in the late 1980s/early 1990s on the basis of what appeared to be not just a convergence of foreign policy interests but political values as well. In the mid-1990s, the Clinton administration embarked on the normalization of U.S. relations with America’s erstwhile adversary, Vietnam, which has developed into a stronger relationship ever since partly on the basis of their common concern about China. In the mid-2000s, the George W. Bush administration and Libyan ruler Muammar Gaddafi turned the previously hostile U.S.-Libyan relationship into a cooperative one partly on the basis of their common concern about jihadist forces which both governments regarded as a threat.

Some of these rapprochements lasted for many years or are still in effect while others were far briefer. More recent U.S. efforts at improving relations with adversaries, however, have either failed to make significant progress or have been reversed by subsequent administrations. The George W. Bush administration’s success in improving ties with Libya ended abruptly when the Obama administration worked with several other governments to bring about its downfall in 2011. The Obama administration’s efforts to improve ties with both Cuba and Iran were reversed by the Trump administration. The Trump administration’s attempts to improve relations with Russia, North Korea, and even (oddly enough) Iran also failed. The Biden administration’s efforts to improve ties with Iran enough to restore the Iranian nuclear accord have so far been unsuccessful, though its efforts to improve ties with Venezuela have been somewhat more so.

This is unfortunate for American foreign policy. The United States now has many adversaries, including formidable states such as China, Russia, Iran, and North Korea, and various jihadist groups. There are also a number of minor adversaries which cooperate with Russia, China, and/or Iran: Syria, Lebanon’s Hezbollah, Yemen’s Houthis, Taliban-ruled Afghanistan, Cuba, Venezuela, Nicaragua, and others still. In the current war between Russia and Ukraine, Iran and North Korea are both supplying arms to Russia while China is supplying Russia with vital economic support.

It would be beneficial for the United States if it could drive wedges among its various adversaries. And there are numerous disagreements and tensions among them that might provide Washington with opportunities for doing so. At present, though, the United States does not seem able—or even willing—to do this. Why? There are several possible explanations.

One identified by Crawford in The Power to Divide is opposition from existing allies to a state offering concessions to an adversary to induce it to alter its behavior. The cases examined by Crawford, though, all occurred either during World War I or just prior to or during World War II. In these cases, the allies in question were all peers or near peers of the state seeking to drive a wedge between adversaries by offering concessions to one of them. Even if the allies were all (more or less) on board, though, such efforts did not necessarily succeed. But opposition from an ally to an effort to woo an adversary made such an effort more difficult to mount due to unwillingness to risk souring relations with or even losing an existing ally in an uncertain attempt to either gain a new one or just to disrupt alliances between one’s adversaries.  Opposition from an existing ally also tended to make a state’s efforts to woo an adversary less credible to that adversary. 

Since the United States has not had peer or even near-peer allies but only smaller allies since the Cold War up through the present, Washington would appear to be in a very different position than that which the allied nations faced during World War I or World War II. Despite this, however, American allies that are by no means equal to the U.S. in military and economic strength have had an outsize influence on undermining recent American efforts to improve relations with adversaries and reducing their ties to more powerful ones. Israel and Saudi Arabia in particular expressed vociferous opposition to the Obama administration’s efforts in conjunction with the UK, France, Germany, Russia, and China to reach a nuclear accord with Iran. Although such an accord was achieved in 2015 despite their opposition, both cheered President Donald Trump’s decision to withdraw from the agreement in 2018 and Israeli prime minister Benjamin Netanyahu has opposed the Biden administration’s efforts at reviving it. A great power whose policies are so subject to influence from its smaller allies will clearly have difficulty in wooing adversaries whom those allies regard as implacable threats—even though improved ties between the United States and an adversary might better serve to reduce the threat from it to America’s existing allies.

Still, small allies can only succeed in disrupting American efforts to take advantage of disputes between adversaries if there is something about the American foreign policymaking process as well as American domestic politics that allows them to do so. And this points to a second explanation, also identified by Crawford, for why the United States cannot successfully pursue wedge strategies: American domestic politics. Improving relations with adversary states is often highly unpopular in the United States. Political forces opposing this are often stronger than political forces supporting it. Allied governments fearing a U.S. rapprochement with an adversary can work with diaspora communities in the United States to oppose it. Diaspora communities from the adversary Washington seeks rapprochement with often oppose it too, especially if they were dispossessed by the regime in power there. Republicans have criticized the Biden administration just for considering lifting some sanctions against Iran and Venezuela in an attempt to change their behavior. (By contrast, Republican efforts to pursue such rapprochements are usually not opposed by Democrats and have had better success in overcoming objections from fellow Republicans.) But as in previous cases (including the Nixon administration’s rapprochements with the Soviet Union and China, the Clinton administration’s normalization with Vietnam, the Obama administration’s nuclear diplomacy with Iran, and even the Trump administration’s efforts to improve ties with North Korea) have shown, Washington has been able in the past to overcome allied and domestic opposition to the pursuit (even if unsuccessful, as in the case of Trump and North Korea) of rapprochements with adversary regimes not undergoing fundamental internal change. Some might argue, though, that heightened political tensions inside the United States in recent years make the pursuit of pursuit or even rational discussion of a host of policy issues more difficult now.

There is, however, a third possible explanation for why the United States is less able now to take advantage of disputes between adversaries than it was in the past: several of America's adversaries have become much more successful themselves at exploiting differences not only between the United States and its other adversaries, but also between the United States and its traditional allies. China’s enormous trade relations with so many of America’s traditional allies have given many of them an incentive to resist isolating Beijing in ways that the Trump and Biden administrations have sought. Many non-Western governments—including all of America’s traditional allies in the Middle East—have largely refused to join America and the West either in condemning Russia’s invasion of Ukraine or supporting Ukraine militarily. Saudi Arabia and the United Arab Emirates not only have maintained good relations with Russia after the start of its war in Ukraine but have recently been pursuing their own rapprochements with Iran.

All of these factors may play a role in explaining why it has seemingly become more difficult for the United States to take advantage of disputes among its adversaries. But while they may be obstacles, they are not insurmountable ones. 

Objections of smaller allies might be overcome if Washington did a better job of explaining what advantages they may receive from the United States improving ties with common adversaries as well as the continuing or even worsening problems that could result if such a policy does not succeed. A firmer U.S. position which warns of the dangers of interfering in U.S. domestic politics as well as points out the inconsistencies between their objecting to American efforts to improve relations with adversaries when they themselves have sought to do so with different or even the same ones would also be in order.