Arms limitation is ridiculously hard to explain and even harder to accomplish. Arms limitation is useful when dealing with bad actors that possess fearsome weapons. If success requires self-limitation as well, the results are often met with derision, since bad actors cannot be trusted. (See U.S. vs. Soviet Union/Russian Federation.) Even when success occurs without self-limitation, the results are subject to withering criticism. (See U.S. vs. Iran.)

Building nuclear weapons is not hard, if states conclude they are necessary and have the money to spend. Building nuclear weapons while seeking to limit the competition is harder. One head of the Strategic Air Command, General Tom Powers, likened this as trying to dress and undress at the same time.

The American public wants to avoid nuclear arms racing but is usually skeptical that successful arms limitation is possible. Success requires negotiation. Skeptics prefer dictation to negotiation. Arms-control negotiations may indeed fail, but dictation will most assuredly fail, even after defeating an adversary on the battlefield. Astatus quo established through dictation fails over time, sometimes leading to another war. (See World Wars I & II.)

Dictation in the guise of negotiation remains an appealing political posture for those who trust combat arms more than negotiations. This has not worked out so well for the United States in the Middle East (see the U.S. vs. Saddam Hussein, Iraq War II), but this hasn’t stopped arms-control skeptics from using this playbook. (See U.S. vs. Iran.)

You can’t always get what you want in warfare or in negotiations. Critics of negotiations sometimes claim that negotiations will end in warfare anyway. Perhaps this explains why critics advocate positions that will stymie negotiations, increasing the prospects for war.

If warfare is inevitable, why not just skip the step of talking that, in the view of critics, is doomed to fail? Because it is impolitic for War Hawks to be that direct. Instead, they find severe fault with U.S. negotiating positions and insist they could strike a better deal. Even while arguing that deal making is a fool’s errand. (Again, see U.S. vs. Iran.)

It is usually safer politically to criticize deals with bad actors than to support them, since the benefits of successful deals become evident many years later, when the criticisms are long forgotten. Can anyone remember the near-apocalyptic arguments offered by opponents of the 1963 Limited Test Ban Treaty that banned mushroom clouds? In this rare case, advocates of the Limited Test Ban not only had persuasive arguments, but also could demonstrate immediate as well as long-term benefits.

The U.S. Constitution stipulates that treaty-making requires a super-majority in the Senate. Consequently, without support from Republican leaders, the Senate’s consent to ratification is unlikely. One manifestation of the crack-up of the Republican Party is that leaders have become followers, choosing to accommodate insurgents. Not one Republican on Capitol Hill supported an agreement that required the expatriation of over 90 percent of Iran’s bomb-making material. None of these naysayers offered a convincing, better outcome to a deal they strongly opposed. Nor did they have to: The burden of successful implementation is on advocates, not opponents, who now offer legislative initiatives that make successful implementation harder.

The Iran deal is a work in progress. It continues to be reviled despite proper implementation to date. It also provides the template for the next administration and its negotiating partners to tackle North Korea’s nuclear program.

Michael Krepon is co-founder of the Stimson Center. This piece originally ran in Arms Control Wonk on June 13, 2016.