When Western policymakers and analysts seek to understand the role of Iran and Russia in supporting Syrian President Bashar al-Assad, the focus is typically on their differences. However, this way of looking at it may be misleading. Russia and Iran are now trapped in a situation of mutual dependence where both stand to lose if the three-way pact between Moscow, Tehran, and Damascus should fall apart. So far, their collaboration has proven effective and they certainly have enough in common to justify a continued aggressive pursuit of joint interests.

To be sure, differences exist. The war’s outcome is indisputably more important for Iran. Tehran views the Syrian government as crucial to its regional security structure, having nurtured a close alliance with the Assad family and its Alawite-dominated security apparatus for over three decades. Ali Akbar Velayati, who advises Iran’s supreme leader Ayatollah Ali Khamenei on foreign policy, has repeatedly referred to Assad as a “red line” for Iran, stressing that “it is none of the Americans’ business to say anything in this regard.” Since 2011, Iran has worked assiduously to shore up its ally, mobilizing thousands of Lebanese, Iraqi, and Afghan Shia volunteers to fight in Syria. When the Russian Air Force intervened in autumn 2015, Tehran ramped up its presence by sending Iranian special forces to the country.

Russia’s approach to Syria is slightly different. It seeks to preserve what is left of the Syrian state over which Assad presides, to prevent Western-backed regime change of the kind so abhorred in Moscow, and to leverage the conflict in its relations with the United States. But it is ultimately a war of choice. While President Vladimir Putin treats Syria as an important issue, it is hardly fundamental for Russia’s national security in the same way that it is for Iran.

There are also slight nuances in how Russians and Iranians approach Assad’s presidency. Iran is explicitly committed to keeping Assad in power. The Kremlin refers to Assad as “the only legitimate president of Syria” and clearly seeks to save his regime. However, it prefers to portray its intervention in terms of defending government institutions and regional stability. “Assad is not an ally for us. Yes, we support him in the fight against terror and in preserving the Syrian state,” Russian Foreign Minister Sergei Lavrov said in early May. “But he is not an ally in the sense Turkey is an ally for the United States.”

Putin places great value on engaging the United States in negotiations, with the current Geneva III peace process being a by-product of American-Russian diplomacy. Moscow has repeatedly pushed Assad to participate in these talks despite his objections to the UN-endorsed principle of a political transition in Syria. According to Western diplomats, Moscow has even said—sincerely or not—that it could envision a peace process that ends with Assad resigning from the presidency.

With the advent of the Geneva talks and a truce brokered by the United States and Russia last February, these differences appeared to grow more salient. While Iran seems only mildly interested in the diplomatic process, Moscow clearly wants Assad to be more flexible. The Syrian government has conceded nothing in Geneva and Assad continues to block food and medicine from reaching rebel-held cities, brushing off Russian and American demands for humanitarian access. This is not making it any easier for Putin to keep his diplomatic game going.

Some Western diplomats now say that their Russian colleagues are becoming visibly frustrated with the Syrian ruler’s intransigence—and with Iran’s habit of nudging Assad back to the battlefield —when the Russians want him to play politics.

A Diplomatic Déjà Vu

If the talk of a Russian-Iranian split over Assad sounds familiar, that’s because we have heard it before. The exact same arguments made the rounds some seven months ago, when Russia first intervened. Then, there was speculation in Western media and policy circles that the Russian intervention would counterbalance Iran’s influence over Damascus. In some cases, these reports were based on anonymous quotes or leaks that may have been deliberately designed to reinforce a belief that Russia’s intervention should not be opposed by Iran’s rivals. For example, Der Spiegel quoted an anonymous Russian diplomat as saying Bashar al-Assad had become “afraid of the Iranians” and needed Putin to pull him out of Tehran’s orbit.

What actually happened suggests a different interpretation of events. In July 2015, the Iranian Quds Force commander Qassem Soleimani reportedly visited Putin in Moscow to prepare for a joint intervention. A bilateral Russian-Syrian agreement legalizing the intervention was signed on August 26, 2015. Iran then opened its air space to Russian planes en route to Syria and began airlifting reinforcements well in advance of the first Russian airstrikes. In late September, the Iraqis announced the establishment of a joint Russian-Iranian-Iraqi-Syrian intelligence coordination center in Baghdad. Bombing began on September 30 and two weeks later Iran launched an offensive near Aleppo under Russian air cover. The following month, Putin flew to Tehran for a meeting with Ayatollah Ali Khamenei, after which the two leaders praised each others’ policies and stressed their “complete agreement” on the Syrian issue.

Of course, this process may have been more improvised than it appears and there may have been secret conflicts behind the scenes. But from the outside, at least, the simultaneous Russian-Iranian escalation in Syria looks a great deal less like hostile competition for influence over Assad than a coordinated intervention in support of a common ally.

Renewed Talk of Iranian-Russian Differences

More than half a year later, both Russia and Iran remain militarily engaged in Syria. Although Moscow scaled down its air raids after a truce was agreed, Putin’s mid-March announcement of a withdrawal was mostly theatre. “Their capabilities are largely the same, or almost identical, frankly,” said a U.S. military spokesperson in May. For its part, Iran remains heavily engaged in Aleppo and other areas, despite American expectations that it would pull its troops back this spring. Iranian casualties continue to mount, indicating that Tehran is still deploying troops to the front.

There is little visible tension. Velayati visited Russia again in February, citing the Syrian war as an example of “the common interests of Iran and Russia,” and in April, Soleimani reportedly returned to Moscow for a tête-à-tête with Putin. Still, the talk of an Iranian-Russian split is now resurfacing. Some have noted Russia’s failure to provide air support for Iranian and Shia fighters in Aleppo. Pro-Iranian factions are said to be grumbling over Russian attempts to steer the Syrian army eastwards against the Islamic State, which they argue does more to improve Putin’s relations with the Americans than to strengthen Assad’s hold on Syria.

Unsurprisingly, rumors have again begun to spread about how Russian-Iranian tension might lead to Moscow or Tehran drifting away from Assad’s side. But this is probably as wide of the mark as the last time around. It is perfectly possible for Iran and Russia to disagree on a great many things and still operate hand-in-glove in Syria. In fact, it is by far the easiest way forward for them both.

Mutual Dependency

Though it may seem counter-intuitive, the fact that Russian and Iranian priorities in Syria do not fully overlap could in fact strengthen their collaboration in the short and medium term.

The Iranians know that Russia’s support for Assad is driven by political calculations rather than national security fundamentals and that Russia is less dependent on Assad’s survival than they are. But from an Iranian point of view, knowing this is more likely to motivate Khamenei to bend over backwards to accommodate Putin, whether by playing along with transitional diplomacy in Geneva—up to a point, of course—or by sending more ground forces to Syria. If Russia were to conclude that the Syrian government is beyond repair, and pull out, Iran would be saddled with enormous additional expenses. Its own outdated air force could never hope to match the effect of the Russian bombing raids, and if veto-wielding Russia strays from Assad’s side, who’s to say what might happen in the UN Security Council?

On the Russian side, things aren’t all that different. In theory, Putin could concede defeat and walk away from Syria, simply to cut his costs, while Iran can not. But after five years in which Putin has taken flak for supporting Assad, the Syrian war is now a matter of great personal prestige for the Russian president. By sending his air force to Syria, he has also put Russia’s military reputation on the line. Still, he now finds himself unable to cash in on his investments unless he works together with Khamenei. Putin has made it clear he will not send Russian soldiers to die in a ground war, but Assad lacks the manpower to keep his slice of Syria under full control, never mind advancing further. If Putin wants the Syrian government to come out on top, he needs the Iranians to keep providing ground troops, just as Iran and Assad need Putin to give them air support.

Indeed, during his visit to Tehran in late 2015, Putin himself lauded Iran’s role and said Russian Air Force operations in Syria would simply be impossible without their participation.”

Iran’s Lack of Options Reinforces Russia’s Alliance with Assad

Given this mutual dependence, Iran’s priorities— supporting Hezbollah, protecting Assad, preventing hostile Sunni groups from gaining power, and curtailing Saudi and American influence in the Levant—will also shape Putin’s options and link Russian strategy more closely to Assad’s survival.

The United States has long tried to convince Russia to help depose Assad through a gradual transition. But unless some fantastic grand bargain is being cooked up behind the scenes, the Kremlin knows that Iran would be very unlikely to go along with such a scheme—not to mention that Assad himself seems determined to stay, or that Russian influence in Syria may be less than meets the eye.

Simply put, forcing a fundamental reordering of the Syrian regime after nearly half a century of Assad family rule would be hard enough if Russia and Iran were working together and Assad complied. If they were instead to work at cross-purposes in the midst of a chaotic war, each wielding one chunk of Assad’s fragmented armed forces, it seems more likely they would split the state and lose the war than achieve anything constructive. For Vladimir Putin, sticking to his battle-tested alliance with Iran and Bashar al-Assad will always remain a safer bet than abandoning them both and hope for a more rewarding settlement with his Western, Arab, and Turkish rivals.

According to American intelligence assessments, the Russian Air Force operates in Syria at “relatively low costs.” Putin’s willingness to stay the course is likely to be cemented by the fact that he can now count on Tehran to continue sending troops to patch up faltering front lines, simply because doing so is the only thing that makes sense from an Iranian perspective. Further sweetening the deal is the fact that Iran is still on the lower rungs of its escalatory ladder and could easily throw in major reinforcements, should necessity or opportunity so dictate. Foreign Policy magazine recently reported that Iranian militiamen are practically falling over each other to get a chance to join the Syrian war, and a report from the Washington Institute for Near East Policy makes clear that Iran has so far only deployed a “tiny slice” of its military power in Syria.

Of course, having the ability to out-escalate your opponents does not necessarily translate into winning a war. Both Iran and Russia have ample reason to worry about being mired in an intractable conflict. Assad’s government is weak and dysfunctional, and at this point neither he nor his allies seem to have a clear endgame in mind.

But neither do their opponents, whose clients in Syria are by any measure much less effective and dependable than the Syrian army. And if Turkey, Qatar, Saudi Arabia, the United States, France, and others, haven’t backed down despite Assad’s recent gains, then there is surely no reason to expect the Iranian-Russian pact to fall apart as long as Moscow and Tehran’s position is improving. Indeed, rather than focusing on the differences between Russia and Iran, which are real but would be mutually damaging to act upon, it seems more meaningful to try to identify their shared interests in Syria, because these are likely to be pursued aggressively.

For more background on this topic, read my recent post Not Just Russia: The Iranian Surge in Syria.