NATO’s strength rests on three attributes of its member states: their commitment, capabilities and cohesion. The United Kingdom’s planned departure from the European Union will affect all three. In the short term, NATO’s productive Warsaw Summit in early July and reassuring statements and defense policy moves from UK Prime Ministers Cameron and May are hopeful. But the probable longer term Brexit scenarios suggest a net negative impact on NATO unless the United Kingdom and other Allies weather today’s populist/isolationist political currents and projected post-Brexit economic fallout to sustain the pledges of solidarity and investments made at Warsaw.

Self-inflicted Self-doubt

The surprise vote for Brexit in the June 23 referendum triggered one of the most volatile political and economic periods in the UK in decades. Within hours, the pound plummeted against the dollar, then-Prime Minister David Cameron announced plans to resign, and it became clear the victorious Leave camp had no feasible post-Brexit plans. The awkward self-consciousness and insecurity that journalist Rob Temple suggests defines the British as a people suddenly appeared also to define them as a nation. For many, the Brexit vote called into question the UK’s identity as a stable, prosperous, globally-engaged European power. Allies and adversaries alike have since looked to London for signals of continued commitment to European security.

Impact on Commitment

NATO’s bold agenda at its July 8-9 Warsaw Summit helped to allay concerns in the near term. With an eye on threats to its east and south, Alliance heads of state agreed on a renewed emphasis on deterrence and collective defense and pledged concrete resources to those goals. PM Cameron reassured leaders in Warsaw that Britain is “not withdrawing from the world, nor are we turning our back on Europe or on European security.” Britain will lead NATO’s Very High Readiness Joint Task Force in 2017. Cameron also announced Britain will serve as a framework nation in NATO’s new deterrence force in the Baltics (deploying soldiers to Estonia and Poland), commit aircraft to NATO’s air policing mission, and continue its deployments to the NATO mission’s in Afghanistan and the Aegean. The UK similarly reaffirmed its commitment to the counter-ISIL Coalition. This includes continued airstrikes in Syria and Iraq, training/advising of local Iraqi and Syrian partner forces, and humanitarian/stabilization assistance totaling over $3.3B for the Syria crisis alone.

Although Cameron’s successor Theresa May reaffirmed these commitments, whether the UK can sustain them in the longer term remains a function of bureaucratic capacity and political appetite. Regarding capacity, it remains unclear how much the eventual negotiation of Brexit and the requisite bilateral trade agreements and other treaties to replace the UK’s EU membership will distract Her Majesty’s Government from other priorities. Ministers are reportedly already sparring over the number of Foreign Office civil servants to be seconded to the new Brexit ministry. More fundamental is the question the UK will face on what sized appetite it has for its post-Brexit global role. Worryingly, the current foreign policy views of the UK’s major opposition parties range from NATO-skeptic to anti-nuclear deterrent to pro-Putin.

Impact on Capabilities

As part of its reassurance campaign, May’s government has hurried to reaffirm several of the planned investments in capabilities detailed in Cameron’s November 2015 Strategic Defence and Security Review (SDSR) and pledged to meet NATO’s benchmark of 2% of GDP for defense spending. In mid-July, the UK parliament voted to renew the UK’s Trident submarine-based nuclear deterrent, and the government announced $5B in deals at the Farnborough air show for sub-hunting P-8 Poseidon aircraft and Apache attack helicopters.

Despite this bullish short term signaling, the UK’s military capabilities in the longer term will hinge on economic circumstances and political appetite. The Organization for Economic Cooperation and Development has projected a post-Brexit UK GDP drop ranging between 2.7-7.7% by 2030. Pro-Brexit skeptics have argued such gloomy scenarios have not yet played out, but that is largely because Brexit has not yet occurred. In the likely scenario of slowed or reverse economic growth, a Tory government may find it hard to resist past instincts to embrace austerity and slash the defense spending promised in the 2015 SDSR. Cameron’s austerity-driven 2010 SDSR left the UK without an aircraft carrier or sub-hunting aircraft and contributed to what one British general termed a “withered” force. (The 2015 SDSR already included some stretches: maintaining NATO’s 2% GDP benchmark required categorizing intelligence systems and military pensions as defense spending, and the SDSR lists Britain’s time zone among the UK’s strategic assets.)

On the monetary front, the Royal United Services Institute has argued that the pound’s historic post-referendum decline relative to the dollar (a 15% depreciation as of October 4) means a projected yearly shortfall of £700M on average annual UK defense imports of £6.5B. Thus both the fiscal and monetary policy consequences of Brexit would potentially threaten the 2015 SDSR’s promised strategic investments (many with U.S. or European vendors) to grow the UK’s fighter aircraft and frigate fleets, increase its expeditionary capabilities, and recruit thousands more troops and intelligence analysts. Separately, should Brexit someday prompt Scotland to leave the UK, it would complicate the UK’s Scotland-based Trident fleet.

Impact on Cohesion

In July in Warsaw, NATO Allies showcased solidarity with the UK, but the longer term consequences of Brexit may test transatlantic cohesion. The surprise Brexit referendum victory has boosted sympathetic populist movements on the continent. Europe faces a fraught electoral calendar over the coming months, with major elections planned in Austria (October), Germany (February), Netherlands (March), France (May), and potentially Spain and Italy. Populist, often far-right parties currently have momentum in many of those contests, with the elections driven by economic and security fears vulnerable to exacerbation by apparent, opportunistic Russian influence efforts. A very different slate of European leaders could emerge from the 2017 electoral gantlet than those that signed the Warsaw Summit communiqué this summer.

In addition, likely contentious Brexit negotiations may strain cohesion among EU leaders. It can be difficult to compartmentalize political disputes and security policy. The UK has traditionally played a bridging role between the EU and NATO/U.S., leading the more transatlantic-minded camp of nations within the EU on issues such as defense cooperation and Russia. Until the day of its departure, the UK will retain its EU vote on any issue requiring consensus or qualified majority voting. But the UK’s voice will diminish as the other 27 members plan the EU’s future without it. This includes recent discussions on improving the EU’s own defense and security capabilities (which, could complement rather than compete with NATO, but only if coordinated properly). An upcoming test of the UK’s continued influence will be the next EU vote to renew Ukraine-related sanctions against Moscow – currently extended through January 31, 2017.

Mull, Britannia

Since the June 23 referendum, the UK government has done an admirable job of reassuring its Allies on NATO and Coalition commitments and capabilities investments. But if the reassuring message out of the Warsaw Summit is to survive longer term headwinds, London must be prepared to redouble those efforts: prioritizing defense spending in the face of economic setbacks, resisting policy distraction, and compartmentalizing intra-EU infighting regarding Brexit negotiations. The exact strategy will require understanding how (or even if?) Brexit will actually unfold, and, more importantly, answering the fundamental question of the UK’s post-Brexit role in the world. It would be Britain’s, Europe’s, and the international order’s loss if the UK were to step back from its traditional positive, outsized global and transatlantic security roles. Lord Hastings Ismay once quipped that NATO’s purpose was “to keep the Americans in, the Russians out, and the Germans down.” Post-Brexit, perhaps to Ismay’s dismay, one might add “to keep the British engaged and relevant.”

Alton V. Buland is currently serving on a detail assignment from the Office of the Secretary of Defense, where he last worked on Europe/NATO policy. The views herein are his own and do not represent those of the United States Department of Defense or the United States government.

The views expressed in this post reflect those of the author and not that of the EastWest Institute.​