Yet for all these advantages, proxy warfare has many risks. Despite the power asymmetry, proxies almost invariably act according to their own interests and impulses. Right after 9/11, the United States asked the anti-Taliban Northern Alliance, its key Afghan ally made up primarily of minorities, not to take Kabul so that a force composed of ethnic Pashtun, Afghanistan’s dominant community, could do so and assuage the fears of minority dominance. The Northern Alliance took Kabul anyway. In 2017, the United States sought to kill Islamic State fighters as its local Kurdish and Arab proxies retook their territory, but the proxy was often pleased to let the fighters slip away from key strongholds like Raqqa and gain the territory without a bloody battle—they wanted the territory, not a high body count. This independence creates a tension for a proxy’s patron. A stronger group is a more effective proxy, but a more effective proxy has a greater ability to hew to its own course.

Such independence often risks dragging the sponsor into an unwanted conflict on behalf of its proxy. Palestinian guerrilla cross-border raids sparked conflicts with Israel, leading to a back and forth that created political pressure on the guerrillas’ erstwhile Arab state supporters who hosted them and at least pretended to support their efforts. Wars in 1956, 1967 and 1982 grew out of these dynamics, with Syria and Egypt being sucked into the fray. Indeed, by giving a group money and support, it may become more reckless, knowing, or at least hoping, that a major power is behind it and would bail it out in the face of trouble.

Proxies are also often corrupt, brutal and incompetent. Just as sponsoring states are happy to fight to the last member of the proxy group, so too are many proxies happy to cash their sponsors’ checks and do little in return. The United States spent millions training various Syrian opposition group members, but in the end only a handful showed up for the fight. Proxies’ brutality may not matter to some: Russia and Iran, gross human rights violators themselves, presumably care little about the abuses of their proxies. The United States, however, is often tarred with the behavior of its proxy, making it difficult to sustain domestic and allied support.

Support for a proxy often leads other states to back their own favored horse, worsening the overall conflict. Lebanon, for many years, saw Iran, Iraq, Saudi Arabia, Israel, Syria and other powers regularly meddle and support rival factions, often solely because one of their rivals was doing so. This, in turn, increased the independence of the proxies as they could threaten to turn to other powers if they felt unsupported.

Once the spigot of cash and weapons to a proxy opens up, it becomes hard to close, particularly for a democracy like the United States. To gain or solidify domestic support for aid, the sponsoring power often talks up the proxy’s cause and the supposedly heroic nature of the fighters, making it harder to walk away from them. Programs and even entire bureaucracies develop, creating vested interests in continuing the fight. Iran’s Islamic Revolutionary Guard Corps (IRGC), for example, is tasked with supporting pro-Iranian revolutionary forces, and as its role outside the country expanded, so too did influence inside. Weak groups and states are often masters of the political dynamics in their patron’s country, manipulating the media and domestic support there to get the sponsor to do their bidding. Pakistan, for example, whips up domestic sentiment against the United States in order to extract a higher price for its cooperation with U.S. counterterrorism efforts.

A state can impose intrusive monitoring and reporting requirements to ensure its proxy does its bidding, but these are often expensive, and in any event, they usually rely on the proxy for information and reduce the level of deniability. Proxies can be pushed, educated or wheedled into better behavior, but too often the United States or other powers can only move the dial a little. States can try instead to choose the “right” proxies, but they are usually few and far between. At times, as in Afghanistan, Iraq and Syria, the United States is usually choosing among different degrees of bad.

THE UNITED States has long worked with proxy forces. Indeed, the very purpose of the legendary Green Berets was unconventional warfare, working with foreign resistance forces against their governments—think organizing Eastern Europeans during a U.S.-Soviet war. A host of other U.S. special operations forces, along with the Marines, elements of the Army and others in the military also regularly work with proxies.

Yet proxy warfare is not at the heart of American doctrine. This is in large part because the United States has a better option: conventional war. However romantic a rag-tag band of guerrillas may be, the smart money is on an Army armored division or Marine regiment. For countries like Iran and Russia, in contrast, conventional war is not always an option, especially when conducted farther from their borders. Not surprisingly, they have incorporated proxies closely into military forces and doctrines. For Iran, the irgc plays a prominent role in the country’s politics and economy, and it is not surprising that they are well-resourced and the tip of the spear of Iran’s foreign policy. Tehran has also long used the formidable Lebanese Hezbollah and its overseas networks to back rebel groups. In addition, by training over 20,000 foreign Shia to fight in Syria, Iran now also has a foreign legion it can deploy to other conflicts. Russia, for its part, now relies on a range of private security actors, ranging from warlords, newly constituted “Cossack” units and the quasi-state mercenary force known as the Wagner Group.

It is also harder for the United States and other democracies to embrace proxies. Russian-backed Ukrainian rebels can use a Russian-provided missile to down a Malaysian plane flying from the Netherlands and kill almost 300 with no outcry in Russia. If a U.S.-backed group did so with American weapons, the outcry would, rightly, be enormous. Thus, the United States is more circumscribed in its choice of partners and the support it will provide them. The Obama administration wrestled for years, largely unsuccessfully, to find a credible anti-Assad force in Syria that had the “right” ideology and no links to jihadist groups.

JUST AS states exploit proxies for their own ends, so too do proxies exploit states—but the cost for them is often heavy. Indeed, just as states are choosing among bad proxy options, so too are proxies often reluctantly working with foreign supporters.

Proxy forces, like the U.S.-backed Kurdish YPG in Syria, the Iranian-backed Houthis in Yemen or Russian-backed forces in Ukraine, seek outside support for many reasons. Resources are the most obvious one: outsiders will provide money, weapons and training, among other forms of support that groups sorely lack. Russian air defense weapons neutralize some of the Ukrainian government’s advantages over rebels. Iranian ballistic missiles enable the Houthis to threaten Riyadh with attacks. And even limited training can give a coherence and level of skill to local fighters that rival militias often lack. Some governments also provide a haven, giving the leadership of a group a place to plan and organize with at least some impunity. Pakistan, for example, allows the Afghan Taliban to enjoy a rear base on its soil where the Taliban’s leaders reside and where the group can organize its efforts to fight the United States and the Kabul government. At times, the military support can be massive. The United States conducted over 10,000 air strikes in Syria, helping the YPG drive the Islamic State from much of eastern Syria—a feat the group could not have accomplished on its own.

In a few cases, outside support may also help a group legitimize itself, though this can be a double-edged sword. Foreign recognition, even from a small state, can burnish a leader’s reputation. This is especially so when the group’s members admire or feel a sense of affinity for the sponsor. For example, Hezbollah gets bonus points as many Lebanese Shia identify with, or at least have a warm feeling for, Iran, the dominant Shia power. The situation is reversed for Palestine Islamic Jihad—a small group Tehran supports to attack Israel, because many among the overwhelmingly Sunni Muslim population of Palestine loath Iran for its support of the Syrian regime and its sectarian war against that country’s Sunnis. Many Syrian groups resisted openly accepting U.S. support in the early years of the war, fearing the loss of their nationalist credibility—even as the Assad regime clung to power and then slowly strengthened its grip.

From a group or leader’s perspective, losing this nationalist credibility can still be worth it because the outside support also offers independence from rivals. Small factions without a broader movement are able to pay higher salaries for members, arm themselves with more powerful weapons, and otherwise distinguish themselves and avoid being swallowed by larger and more powerful groups. As such, the outside support may help the group at the expense of the movement as a whole, allowing divisions to grow and fester.