The P5+1 and Iran finally reached an agreement on the Iranian nuclear program this week:

Iran reached a landmark nuclear agreement with the U.S. and five other world powers, a long-sought foreign policy goal of President Barack Obama that sets the White House on course for months of political strife with dissenters in Congress and in allied Middle Eastern nations.

A final, comprehensive nuclear deal with Iran is a real success for the U.S. and the other members of the P5+1. Even if a deal had not been reached, the negotiations over the last two years had demonstrated the potential of engaging Iran directly in diplomacy. Now that these negotiations have definitely borne fruit, there may be a chance for continued engagement with Iran on other issues. There is no guarantee of that, and there is enormous opposition to making the effort, but it would be worth attempting. While there has been a fair amount of speculation about a coming detente with Iran, that will depend on how current and future governments in Washington and Tehran decide to use the opening that this deal provides.

The next and most important step will be implementing the agreement on both sides, and there will be constant pressure from hard-liners to find excuses to scrap the agreement in the months and years to come. Concluding the deal doesn’t mean that the efforts to sabotage and blow it up will end. On the contrary, we can expect redoubled effort from Iran hawks that have so far been unable to block a deal. Having failed to derail the deal, hard-liners will still be eager to take advantage of any weaknesses in the deal to try to wreck it.

The WSJ report summarizes the contents of the deal:

At the heart of the agreement between Iran and the six powers—the U.S., U.K., Russia, China, Germany and France—is Tehran’s acceptance of strict limits on its nuclear activities for 10 years. These are supposed to ensure that the country remains a minimum of 12 months away from amassing enough nuclear fuel for a bomb. After the 10-year period, those constraints will ease in the subsequent five years.

This will limit Iran’s nuclear program more effectively than a decade of sanctions and coercive methods ever did, and it makes Iran’s acquisition of a nuclear weapon much less likely than any other available course of action. The alternatives that Iran hawks have been proposing for the last two years–ending negotiations, more sanctions, threatening or taking military action–would have left Iran’s program under fewer constraints and would have pushed Iran towards building nuclear weapons. It is important to remember that the loudest, shrillest opponents of this deal would have made a nuclear-armed Iran more likely if they had their way. So when the hard-liners start their inevitable cries of “appeasement” and “surrender” start, keep in mind that their “solution” would have failed and backfired as usual. If the deal is implemented fully, this should take the nuclear issue with Iran off the agenda for at least the next decade and possibly much longer than that.

It is too early to know how the deal will affect internal conditions in Iran, but it is probable that Rouhani’s success in these talks will give him more room to push for some measure of economic and social reform. Sanctions relief will take some of the economic pressure off of the Iranian people, and especially the Iranian middle class, and that will gradually aid the cause of Iranian opposition groups that the sanctions have been helping to strangle. There aren’t likely to be any dramatic changes in Iran’s internal politics, but reducing sanctions can only help loosen the grip of the regime and the hard-liners that they have strengthened in the past.

This is a significant achievement by the Obama administration, and Obama and Kerry deserve credit for persevering and seeing the negotiations through to this point. It would have been extremely easy for Obama to buckle under domestic political criticism, and in this instance he didn’t end up yielding to what his hawkish detractors demanded. When it comes to arms control and nonproliferation, Obama has often been much more willing to take risks than on many other issues, and he has done so again here. A president less committed to nonproliferation probably would not have supported these talks for this long, and an administration that was less interested in diplomatic engagement would never have started them in the first place.

The future success of the deal will depend on support and compliance from the next administration, so it is not guaranteed that the U.S. will keep up its end of the bargain after 2017. When many of our Republican presidential candidates vow to scrap the deal as soon as they are in office, we should take them at their word. Scrapping the deal would be costly for the U.S. and would scandalize our major allies that have worked with our government to conclude the agreement. We can hope that even a very hawkish president would come to recognize the folly of undoing a deal with Iran in the future, but that isn’t something anyone should count on.