A historic something has just happened. In a deal struck in Vienna, the government of Iran has agreed that “under no circumstances will Iran ever seek, develop or acquire any nuclear weapons.” In return, most international sanctions on Iran will gradually be lifted.

For U.S. President Barack Obama, this may be the crowning foreign policy achievement of his presidency. “Today after two years of negotiations, the United States, together with our international partners, has achieved something that decades of animosity has not: a comprehensive long-term deal with Iran that will prevent it from obtaining a nuclear weapon,” the president said in a speech after the agreement was signed.

The White House calls the Vienna agreement a “historic deal” and historic certainly seems to be the adjective du jour—on all sides of the debate. For example, the European Union High Representative Federica Mogherini labeled July 14 a “historic day” and U.K. Foreign Secretary Philip Hammond celebrated it as a “historic agreement,” while Iranian Foreign Minister Mohammad Javad Zarif preferred the term “historic moment.”

Taking the opposite view, Israeli Prime Minister (and Foreign Minister) Benjamin Netanyahu considered it a “historic mistake.” Other Israeli politicians chimed in with similar denunciations, such as Deputy Foreign Minister Tzipi Hotovely, who called the deal a “historic surrender.” But Israel’s hard-line Minister of Education Naftali Bennet mixed up the vowels and had a hysteric reaction instead, warning that Iran’s next step may be to annihilate London and New York.

Meanwhile, Middle East commentator, former U.S. diplomat, and man of many nuances Aaron David Miller has opined that the deal is neither a “historic catastrophe” nor a “historic transformation.”

In Syria, where the Iranian government serves as a main prop for President Bashar al-Assad’s embattled government, the opposition is predictably unhappy with the news. But the president himself is jubilant—and he swiftly fired off a congratulatory telegram to Iranian Supreme Leader Ayatollah Ali Khamenei in which he lauded the “historic achievement.”

Will Assad Get More Guns?

Russia and China are now both angling to get into the Iranian arms market, which is sure to swell once oil money starts flooding back into government coffers in Tehran. Some commentators have estimated that Russia could be looking at $13 billion in arms export earnings and no one will be shocked to learn that the Kremlin has been pushing to lift arms sanctions immediately after an agreement.

The Iranian arms trade matters a great deal to Syria. While Khamenei’s top priority is of course to improve Iran’s own defenses, recent years have proved that Iran sees its own security as inextricably tied to the network of regional allies and proxies it has cultivated in Syria, Iraq, and Lebanon over the past decades. These allies include Assad and several Syrian pro-government militias, but also the Lebanese Shia faction Hezbollah and Iraqi Shia militias that fight in both Iraq and Syria. Having spent billions in support of its regional allies even as its economy suffered from crushing international sanctions, Iran isn’t likely to hold back now.

Disagreements over conventional arms sanctions were reportedly the very last issue left on the table as the Vienna talks reached their final stages. American allies such as Saudi Arabia had flagged this as a key issue as had the U.S. military. In an unusually blunt political recommendation, the chairman of the Joint Chiefs of Staff, General Martin E. Dempsey, had declared that “under no circumstances” should the nuclear deal be allowed to “relieve pressure on Iran relative to ballistic missile capabilities and arms trafficking.”

Iran, on the other hand, has been eager to play up the benefits of a deal for its allies, with its negotiators recently telling the media that an agreement would allow Tehran to “continue supplying defensive weapons to its regional allies to fight against terrorism and extremism.” That’s not likely to be the U.S. view—but the key word here is “continue.” For years already, the Iranian government has been flouting sanctions by transferring arms and military expertise to Assad’s army and its other regional allies. Sanctions may have prompted a certain degree of discretion, but they have hardly affected the trade itself. What they may have done is make purchases more costly and prevent Iran from acquiring certain top-of-the-line products for its allies.

Will that change now?

According to President Obama’s description of the deal, arms sanctions will not be lifted immediately. Instead, they will be phased out gradually as Iranian compliance is monitored over several years. “Iran must abide by the deal before additional sanctions are lifted,” the president said in his White House address, “including five years for restrictions related to arms, and eight years for restrictions related to ballistic missiles.”

Moscow’s Missile Deliveries

Still, in some ways, Iran’s military is already benefitting from the deal. In April, Russian President Vladimir Putin pointed to progress in the nuclear talks as his reason for lifting a ban on sales of the S-300, a powerful air defense system long sought by the Iranians as a means of offsetting Israeli and American air superiority.

Iran recently claimed to have invented its own locally produced version of the S-300, but this was mere propaganda—evidenced by the fact that Tehran’s ministry of defense has continued to pine for the Russian-made original.

Syria, too, has been seeking completion of a pre-2011 deal to purchase the S-300, after it was blocked in mid-delivery by Moscow, ostensibly on economic grounds. Whether the gradual unlocking of international sanctions against Iran will change matters for Assad’s procurement efforts remains to be seen.

A Stronger Iran Is a Stronger Assad

For Assad, then, the Vienna deal isn’t likely to result in immediate deliveries of military hardware. But it is likely to ensure the growing financial and political clout of his most reliable ally.

Iran-backed Shia militias already play a major role in Assad’s defenses in several areas of Syria, with Hezbollah fighters very prominent in the current offensive against the city of Zabadani. Iranian military advisers have also long been present in the country, and Iran is reportedly a main funder of the National Defense Forces militia network, which has helped fill the gap left by Assad’s shrinking army since 2012.

But Iran’s economic and logistical contributions to Assad’s war efforts may be even more important. Iranian political contacts, organization, and financing underpin the oil tanker traffic keeping Assad’s economy, infrastructure, and power generation abilities afloat. Iranian financial backing and aid shipments have enabled purchases of oil as well as other key imports. As recently as May 19, Iran and Syria signed a new deal for a $1 billion credit line, giving Assad’s failing economy another lease on life.

Simultaneously supporting Assad, Hezbollah, the Iraqi government, and various Kurdish, Palestinian, and other allies is an exceedingly costly project for Iran. In particular, Syria has emerged since 2011 as a bottomless pit into which Iran is shoveling its own hard-earned oil and taxpayer money by the billions. During the past few years of sanctions-induced economic distress, many ordinary Iranians seem to have begun grumbling over these costs. That’s why financial and oil sanctions relief matter so much to Assad. More money for Iran means more money for Syria, or at least less Iranian domestic pressure to trim the current level of funding.

And with wealth comes flattery. Iranian markets will now open up again after the lean years of the sanctions regime, and the government will have cash on hand to order in big infrastructure restoration projects. Many current and former trading partners (surely including some EU members) can be counted on to soften their objections to Iranian regional policies if that’s what it takes to get a piece of the pie. It is possible, indeed quite likely, that this could help Iran promote its own understanding of the Syrian war.

Assad clearly hopes that it will, lauding the Vienna deal as a “fundamental turning point” in Iranian relations with the rest of the world.

Will the Deal Change Iran?

In the conspiratorial world of Syrian politics, speculation is rife about secret “Syria clauses” in the deal. The opposition fears an under-the-table deal benefiting Iran and Assad, while government supporters are afraid that Iran will now move to improve its relations with the West by sacrificing Assad. Neither seems very likely and negotiators are probably correct when they claim that the Vienna process focused exclusively on the nuclear issue. But it is no secret that there are those on both sides who would like to see a more comprehensive rapprochement, or at least improved coordination in the struggle against the extremists of the self-proclaimed Islamic State.

With the nuclear deal now signed and perhaps secure, there is suddenly room for new talks to begin. Or if they are already secretly under way, such parallel diplomatic tracks can be accelerated without fear of upsetting the nuclear talks. Whatever happens, Iraq and Syria will be top concerns for all involved, although the former may make for more fruitful discussions than the latter.

In pushing so hard for the nuclear deal, Barack Obama has seemingly wagered that some combination of trade and talks will be more successful at incentivizing U.S.-friendly Iranian politics than the isolation and military threats of the past decades. Whether he is right or wrong, it is not an unreasonable assumption. For Assad, too, today’s celebration must therefore be tinged with quiet concern over how an improvement in Iranian-Western relations might affect Tehran’s political priorities in coming years. A historic achievement this may well have been, but history has a way of unfolding at its own pace and in its own ways.