On June 23, 2016, Britons went to the polls to vote on whether the UK should remain in the EU or leave the bloc. The “Leave” camp’s narrow win has resulted in bedlam, not only for the UK’s relations with the EU and transatlantic community, but also for the world economy. Yet looking at the longer-term picture, it is just as important to consider the implications for security and diplomacy in the Asia-Pacific region. In this regard, the Five Power Defence Arrangements (FPDA), comprising the UK, Malaysia, Singapore, Australia and New Zealand, has been a central component of British involvement in the security of the Asia-Pacific. Now, faced with a more insular senior partner entering a period of economic and political uncertainty, the other four members of the Commonwealth-based security pact will likely begin to question their future and look to the United States.

Britain’s security cooperation in the Asia-Pacific has generally been overlooked in favor of America’s hub-and-spoke system of alliances. The Brexit vote may well lead to a point of no return in terms of the incremental downsizing of British security cooperation in the region. While the governments of Britain’s FPDA partners have been quick to downplay any impact of the Brexit vote in their relations with the UK, it is necessary to look beyond diplomatic platitudes. During World War II, British preoccupation with the European and North African theaters came at the cost of providing effective air and naval forces for the defense of Malaya and Singapore. The psychological impact of the Japanese victories in Malaya and Singapore cannot be understated—history books in both countries continue to emphasize this period of history as a rationale for strong national defense.

The fact that the United States bore the brunt of the Pacific campaign against Japan factored into the post-1945 strategic planning of Britain’s aforementioned Commonwealth partners. As early as 1951, Australia and New Zealand entered into the ANZUS Treaty with the United States out of fear of Communist expansion. Even as the British pullout from the Asia-Pacific got underway, Australia and New Zealand increased their own alignment with the United States, most visibly by deploying combat troops to support the American involvement in Vietnam. Singapore had similar fears and, from the 1970s onwards, promoted itself as what Daniel Chua termed a “Good Nixon Doctrine” country seeking to achieve military self-reliance for its own security, yet open to a high level of security cooperation with the United States.

Under such circumstances, should Britain formally withdraw from the EU, the long-term fallout of a Brexit would likely lead to Britain’s FPDA partners’ forging new security arrangements with the United States. Such a scenario may occur due to the following two factors: first, that a British withdrawal from the EU will undermine the overall credibility of Britain’s ability to project power abroad; second, that the domestic pressures that led to the narrow victory of the Leave campaign are a sign of a Britain that is more inward-looking, and less willing to shoulder the burden of its overseas alliance commitments.

Projecting Power After Brexit

The long-term credibility of Britain’s global power-projection capabilities is coming under increasing doubt. This was evident in the British Ministry of Defence’s (MOD) 2010 Strategic Defence and Security Review (SDSR), which saw a 7.7 percent cut in defense spending for four years. Among the defense-spending casualties, the landing platform dock HMS Albion was removed from the Royal Navy’s front line to undergo extensive refit, as was the second unit of the Queen Elizabeth II–class carrier. The Royal Navy’s Harrier STOVL aircraft was retired (and budgetary wrangling continues to stall the procurement of F-35 fighters). Each Vanguard-class submarine’s weapons loadout was reduced from forty-eight nuclear missiles to forty, along with the reduction of Britain’s nuclear arsenal from 160 warheads to 120.

Defense cutbacks cast serious doubt over Britain’s ability to project power abroad. Tellingly, Adm. John Woodward, who commanded the British Naval Task Force that retook the Falkland Islands in 1982, warned in 2012 that, in the event of another Argentinian invasion, “We could not retake the Falklands. We could not send a task force or even an aircraft carrier.”

Although the 2015 SDSR was something of an improvement, the overall direction of British defense policy is oriented towards threats to the British heartland. The 2015 SDSR identified low-intensity threats like terrorism as Britain’s foremost security concern, with only passing references to “state-based threats,” “intensifying wider state competition” and “the erosion of the rules-based international order.” Growing tensions in the South China Sea, Russia’s support for both the insurgency in eastern Ukraine and the Assad regime in Syria, and British operations against the Islamic State all demand London’s attention.

If anything, the MOD’s already over-stretched resources are likely to be further impacted in the event of a second Scottish independence referendum. First Minister Nicola Sturgeon’s response to the Brexit vote was telling:

“Scotland faces the prospect of being taken out of the EU against our will. I regard that as democratically unacceptable. . . . For many people the supposed guarantee of remaining in the EU was a driver in their decision to vote to stay within the UK.”

The prospect of a “Scottish exit” from the UK is a very real one. Scotland’s GDP in 2015 was estimated at $233 billion, or 8 percent of the UK’s total GDP. Scotland’s 5.3 million people constitute 8.3 percent of Britain’s population of sixty-four million. Furthermore, oil production in Scottish waters constitutes an estimated 96 percent of the North Sea total. A Scottish exit from the UK will have a further knock-on effect on the British economy. A Scottish exit could also compromise the British nuclear arsenal, which is deployed onboard submarines operating from Her Majesty’s Naval Base, Clyde.

Northern Ireland also voted to remain in the EU. Deputy First Minister Martin McGuinness has called for a referendum on Northern Ireland’s independence from the UK and unification with the Republic of Ireland. Such political and territorial disintegration of the UK would damage its political credibility beyond repair.

Can an economically and politically diminished Britain maintain credible power-projection capabilities in addressing overlapping security flashpoints around the world? Not likely. While it is too early to make cast-iron predictions, it is possible to imagine a scenario in which Russian and Chinese leaders agree to coordinate territorial expansion in their respective geostrategic neighborhoods in a bid to force the transatlantic community to divide its scarce resources. It is possible to imagine Britain responding to such a scenario as it did during World War II—by neglecting its security interests in the Asia-Pacific.

The Brexit vote is indicative of an emerging “Little Britain” mentality. This sentiment reflects a narrow sense of inward-looking British nationalism that rejects the forces of globalization and the notion of Britain participating actively in the international community. The “Little Britain” mentality is concerned with issues such as the underfunded National Health Service, the impact of immigration on the UK’s labor market and perceptions that migrants are undermining the “Britishness” of the nation. Growing numbers of Britons have little interest in supporting overseas military operations at a time when more pressing, immediate domestic issues have been successfully capitalized on by the Leave movement. Under such circumstances (and also taking into account the likely damage to the British GDP and defense budget), the possibility of a Britain unable or unwilling to fulfill its commitments to the FPDA is something that defense planners in the region will have to take seriously.

Whither the FPDA?

Britain has historically been the keystone of the FPDA. As the only member with a nuclear arsenal, the central assumption of FPDA planners at the time of its founding was that British air and naval power, operating from bases in Malaysia and Singapore, would contain Communist expansionism. Even after the downsizing of British military deployments east of the Suez, the regional character of security challenges in Southeast Asia during the Cold War meant that a scaled-down British military presence during the 1970s did not lead to panic amongst its FPDA partners.

Present day Southeast Asia is a security environment simultaneously more benign and more dire than during the Cold War. It is more benign given that the region is not faced with the ideologically driven nature of Soviet expansion. Instead, the most pressing contemporary security concern for the FPDA stems from China’s increasingly assertive claims to portions of the South China Sea. This too does not directly infringe on the interests of the FPDA, given that the only one of its members to have territorial disputes with China is Malaysia, over the Luconia Shoals. Thus far, there has been little antagonism between China and Malaysia over the issue.

At the same time, the potential security challenge posed by China is more dire than any posed to the region during the Cold War. As part of its strategy to counter a U.S. military intervention in the western Pacific, China has developed an Anti-Access/Area Denial strategy (A2/AD) based on the use of long-range cruise missiles, surface-to-air missiles, submarines and naval mines to close down Sea Lines Of Communication (SLOCs). China’s recently upgraded DF-31A cruise missiles have a range of 11,200 km and are capable of targeting the whole of Southeast Asia, along with most of Australia. In other words, China, in acquiring the ability to deny critical SLOCs to the U.S. Navy, has also acquired the capability to shut down the same SLOCs upon which regional maritime commerce depends.