The Trump administration has articulated an ambitious new vision for nuclear arms control, one that includes China and seeks to limit more types of Russian systems. This vision appears to have little room for the New START agreement, which helped to cap U.S. and Russian nuclear arsenals and which is due to expire in 2021. And yet there is little in the public record to indicate how the administration would deal with various problems that would surface if New START is left to die.

In June, eight leading Democrats on national security sent a letter to President Trump asking seven questions about his arms control agenda and how it might be brought to fruition. Several of those questions remain unanswered — at least by the Trump administration. But we can offer some answers, thanks to a recently released CNA study we conducted looking at potential risks and options after New START:

“If Russia were to increase the size of its strategic nuclear arsenal, how would the United States respond?”

Unlike in 2009 and 2010, when New START negotiations were underway, Russia is vigorously modernizing its nuclear arsenal. If the treaty expires, Russia could in short order exceed its limits by hundreds of deployed warheads. The United States would then have two options.

First, it could follow Russia past New START’s limits on deployed warheads and delivery vehicles; for example, by re-adding missiles and warheads to its Ohio-class ballistic missile submarines. But this kind of nuclear re-arming would take time, cost money, and could fuel the global perception that the United States and Russia are entering a dangerous new arms race.

Or the United States could stay at New START levels regardless of Russian increases. The current arsenal, which combines ICBMs, sub-launched ballistic missiles, and bombers armed with gravity bombs and cruise missiles, would remain sufficient to deter limited and large-scale nuclear attacks, assuming the current modernization program of record remains intact. For example, even if Russia maxed out its upload capacity and launched a surprise attack, it would exhaust most of its deployed forces on U.S. ICBMs, thus leaving it with no confidence it could deter the United States from responding with the roughly 450 warheads it would have remaining on the Ohio submarines at sea.

But this would break with the longstanding U.S. policy of maintaining rough numeric parity with deployed Russian strategic warheads. Given that the Trump administration’s central critique of New START is that it does not help narrow the large asymmetry between U.S. and Russian non-strategic nuclear weapons, it seems unlikely that the administration would countenance an asymmetry at the strategic level.

Both of these options have pros and cons. The Trump administration clearly hopes to avoid a scenario where it would have to choose between them, as its goal is to replace New START with a better treaty. Yet February 2021 is only eighteen months away, and it is highly unlikely the administration will achieve its preferred trilateral agreement before then. Thus, unless the administration extends New START, it must prepare to face a decision about how to respond to an increase in Russia strategic forces.

“What is the assessment regarding the potential loss of insights into Russia’s nuclear forces if New START expires?”

Without New START, the U.S. intelligence community would have less insight into Russian strategic nuclear forces. The agreement’s verification regime provides U.S. analysts with a granular understanding of Russian forces through data exchanges, notifications, and on-site inspections. For example, the treaty requires Russia to notify the United States 48 hours before any new ballistic missiles leave the production facility, then tell the United States where it stations the missiles and whether they are loaded into launchers. If Russia pulls older missiles from deployment and eliminates them, it must notify the United States and follow a verifiable procedure for functionally disabling them. Similar to data gathered through consumer purchases and social media, each individual piece of information is only of limited value, but when combined they create a deep window into Russian nuclear operations.

The United States will certainly have some ability to acquire this information through its independent means of intelligence gathering, but at a higher cost and with less certainty because Russia will not be telling the U.S. intelligence community where and when to direct its national technical means, such as satellites, and what activity it will be observing.

And there is some information the United States receives from Russia through New START that it simply will not be able to acquire through other means. For example, twice a year Russia provides the United States with the total number of deployed strategic warheads, their breakdown across deployed ICBMs and SLBMs, and how many warheads are deployed on delivery vehicles at each ICBM and SLBM base.

“What resources will be diverted by the U.S. Intelligence Community to fulfill this mission?”

Without the data provided through New START, demand for analysis on Russian strategic nuclear forces will increase. To fill this demand, the United States would need to divert both national technical means and the analysts who make sense of raw data from other priorities, such as Chinese, North Korean, and Iranian ballistic missile programs.

Indeed, the treaty was signed in part to avoid having to make such tradeoffs. In 2010, Gen. Kevin Chilton, the commander of U.S. Strategic Command, said that without New START, the United States would “be required increasingly to focus low density/high demand intelligence collection and analysis assets on Russian nuclear forces.”

“What would be the effect on our alliances around the world, especially NATO, of letting the Treaty lapse?”

Nuclear arms control with Russia also helps to unite U.S. allies in NATO around a common security strategy. According to Robert Bell, the former U.S. defense advisor to NATO, the United States’ continued commitment to arms control was essential for garnering a consensus within the alliance at the 2016 Warsaw Summit and the 2018 Brussels Summit.

While NATO allies ultimately supported U.S. withdrawal from the Intermediate-Range Nuclear Forces Treaty, they are unlikely to rally around the United States if it allows New START to expire despite Russian compliance with the treaty. What is more, if U.S. allies perceive the United States as failing to put forward a serious nuclear risk-reduction strategy, sustaining NATO solidarity in the future may become more difficult. Some NATO members have domestic constituencies who are skeptical of NATO’s nuclear burden-sharing mission. These policy preferences may gain greater traction in a post-New START world, especially if both the United States and Russia are increasing their deployed nuclear forces and the end of U.S.-Russian arms control increases discord within the already strained Nuclear Non-Proliferation Treaty.

Recommendations

The Trump administration is correct that United States must broaden its approach to arms control. Verifiable limits on strategic nuclear forces remain valuable, but the spectrum of weapons and actors that could trigger arms competitions and nuclear conflict has expanded beyond the narrow U.S.-Russian arms control framework. This is why the Trump administration should extend New START. Extension would preserve verifiable limits on Russian strategic nuclear forces while the United States develops new proposals tailored to 21st-century nuclear dangers.

Moreover, the administration should act promptly. Leaving New START extension unresolved into next year is likely to reduce the administration’s ability to achieve its arms control objectives. The closer we get to February 2021, the more attention U.S. defense, intelligence, and diplomatic officials will likely devote to figuring out how to manage the challenges that would emerge without New START — and the less they will have to conceptualize and negotiate new and plausible arms control arrangements for the emerging strategic landscape.