There are several things to consider when digesting news about the recently signed nuclear limitation agreement between Iran and the P5+1 countries (the UNSC permanent members US, UK, France, China and Russia plus Germany, with the EU as a mediator/facilitator). First, what is publicly announced about international agreements is not always all that is agreed upon. Often times what is not publicly disclosed is as or more important than the announced terms.
Second, actors given majority credit for an international agreement may not have been as decisive as they and their home media would like the public to believe.
Third, no agreement stands alone or occurs in a vacuum: other geopolitical and strategic considerations are bound to frame and influence the terms of the finalized compact.
The agreement between Iran, EU and six world powers on the conditions by which Iran would de-weaponize its nuclear research program in exchange for a temporary relief from international sanctions is a case in point. The agreement is for six months, with an eye to negotiating a more permanent contract at the end of that period. The 7 billion dollars in sanctions relief is not a huge amount by global standards, but significant in that it demonstrates the effectiveness of the sanctions regime imposed on Iran as well as its the flexibility of it (since it can be reimposed in the event Iran reneges on its promises).
The technical details are pretty straight forward: Iran agrees to suspend the enrichment of natural uranium (U238) beyond five percent and to neutralize its stockpile of 20 percent enriched uranium (U235). This is a step away from weaponization because most weapons grade U235 is enriched above 80 percent, which is relatively easy to produce if 20 percent enriched U235 is on hand. Most civilian nuclear energy programs use 3 to 5 percent enriched U235 fuel, thereby making weaponization more time consuming and costly. The agreement therefore does not interfere with Iran’s ability to enrich uranium for civilian power production.
Iran will also curb its use and purchase of centrifuges employed for said enrichment as well as suspend the heavy water reactor extraction methods used to produce plutonium. The entire Iranian nuclear complex will be placed under tighter international inspection controls.
The Western media has variously described the deal as a “US-Iran” or “Iran-Western” accord, but the importance of China and Russia should not be ignored. Both of these powers have friendly relations with Teheran and have supplied it with weapons and diplomatic support. They were not at the meetings in Geneva to serve as props for the US and UK. In fact, their presence in the negotiations should be considered to be decisive rather than incidental, to the point that they may have had a large say in the broader issues being bargained over that eventually sealed the deal.
What might those issues be? That brings up the larger geopolitical and strategic context.
Iran, as is well known, is a major patron of the Assad regime in Syria, currently engaged in a civil war against a Sunni opposition backed by the West and Sunni Arab states. The Assad regime receives funding, weapons and direct combat support from the Iranian Revolutionary Guards and Hizbollah, the Lebanese Shiia militia that serves as an Iranian proxy and power multiplier in the Levant. Assad also receives weapons from Russia, which has a naval base at the port of Tartus and which considers the Assad regime as its closest Arab ally.
Should Assad fall, not only Russia but more importantly Iran will lose a major source of power projection in the region. This would suit Israel and the Sunni Arab world, as Iran is seen as an existential threat by Israeli and Arab Sunni elites alike. Defeating Assad will pave the way for Israel to turn its military gaze more directly on Hizbollah, something that will not meet with much opposition from the West or the Sunni Arab elites. Israel is less concerned about the radical nature of a future Sunni government in Syria or the fragmentation of that country into sectarian enclaves, as the heterogenous rebel coalition now fighting Assad will be consumed by factional in-fighting that will limit its ability to project meaningful military force across its borders whether Syria as presently constituted remains intact or not. Sunni Arab elites will welcome a Sunni dominance in Syria as another bulwark against Shiia influence in the eastern Mediterranean, again, whether Syria retains its present boundaries or divides into smaller Sunni states.
However, it has become increasingly clear that the leading rebel groups in Syria are led by al-Qaeda inspired jihadis who are as bad if not worse than the Assad regime when it comes to committing callous atrocities against civilians as well as armed opponents. They are people who do not have much regard for the laws of war and who have published videos of themselves gassing dogs using crude chemical weapons (which may have had something to do with the rush to reach agreement on removing Assad’s CW stockpiles in the midst of the civil war), and who have had to apologize for “accidentally” beheading a fellow Sunni rebel leader under the mistaken assumption that he was an Alawite or Shiia Assad supporter (all videotaped, of course). Their atrocities (as well as those of the Assad regime) are well documented in the propaganda war now raging on social media.
Jihadist government in Syria may not be an existential threat to Western, much less global interests, but it is the most visible. It would be the first and most important place outside of Afghanistan where Islamicists fought their way into power (Somalia does not count). That is a significant issue regardless of their actual military power because symbolism matters and diplomacy is as much about symbology as it is about substance.
Following Russia’s lead and over Israeli and Saudi protestations, Western powers have become very alarmed about a possible jihadi victory in Syria, and now see a weakened Assad remaining in power or as part of a brokered coalition as the lesser evil. Hence the previous Western moves to give material and technical assistance to the rebels have slowed considerably while calls for a negotiated solution grow louder. Not surprisingly and following on the success of the Iran nuclear accord, negotiations on the Syrian crisis are now scheduled for January in Geneva, and include the Iranians as interested parties along with those supporting the anti-Assad forces grouped in and around the non-jihadist Syrian National Coalition and Free Syrian Army.
For Iran, this was the bargaining chip. It can agree to temporarily halt its nuclear enrichment efforts in exchange not just for sanctions relief but also in exchange for a reprieve for Assad. As things stood, its nuclear program invited massive preemptive attack and Assad’s fall spelled the end of its geopolitical influence. By agreeing to curtail its nuclear program to verifiable peaceful uses in exchange for a withdrawal of Western aid to the Syrian rebels and sanctions relief, Iran is able to buy Assad enough time to defeat the rebels, thereby maintaining Iran’s influence as a regional power while it re-builds its domestic economy unfettered by sanctions. Israel and the Saudis may not be happy about this, but their narrow interests have been shown to not be coincident with those of their Western allies on a number of strategic issues, Iran being just one of them.
Political scientists would call this the nested game scenario: within the public “game” involving negotiations between Iran and its foreign interlocutors lie other confidential or private “games” that are key to resolving the larger impasse over its nuclear program (Iranian involvement in Iraqi domestic politics might be another). These games are defined as much by those who are excluded as those who are involved in them.
All of this is speculation, and any “nested game” deal on Syria would be part of the non-public aspects of the agreement  and therefore deliberately non-verifiable over the near term absent a leak. But there is enough written between the lines of the public rhetoric to suggest that this may be what is at play rather than a simple compromise on the limits of Iran’s nuclear ambitions.