In the last year, some 39,000 migrants, mostly from North Africa, tried to make their way to the United Kingdom from the French port of Calais by boarding trucks and trains crossing the English Channel. In response, the British government attempted to secure the entrance to the tunnel in Calais, dispatching two and a half miles of security fencing that had been used for the 2012 Olympics and the 2014 NATO summit.

The United Kingdom’s improvised response to the migrant crisis, with recycled fences substituting for a coherent immigration policy, is emblematic of its increasingly parochial approach to the world beyond its shores. The Conservative government of Prime Minister David Cameron appears to lack a clear vision of the country’s place on the global stage. The United Kingdom, a nuclear power and permanent member of the UN Security Council, now seems intent not on engaging with the outside world but on insulating itself from it. The United Kingdom does not merely lack a grand strategy. It lacks any kind of clearly defined foreign policy at all, beyond a narrow trade agenda.

Historically, the United Kingdom has been an active player in world politics. After the loss of its empire, the country was a founding and engaged member of the institutions of the postwar Western order. British governments have led the way in pressing for, and undertaking, humanitarian interventions from Sierra Leone to Kosovo. And the United Kingdom’s relationship with the United States has been a great asset to both sides since World War II.

Recently, however, factors including fatigue following the wars in Afghanistan and Iraq, a recession, and a prime minister with little apparent interest in foreign affairs have conspired to render the British increasingly insular. The British diplomatic corps and military have seen their capabilities slashed amid harsh austerity measures. In its limited contribution to the campaign against the self-proclaimed Islamic State (also known as ISIS), in its mercantilist approach to China, and in its inability to formulate a real strategy to respond to Russia’s aggression in Ukraine, the United Kingdom has prioritized narrow economic interests to the detriment of broader considerations of international security.

With a national referendum on the United Kingdom’s EU membership likely to be held in 2016, debates about the country’s place in the world will come into sharper focus. What exactly is the United Kingdom capable of achieving when acting alone? Should London work with partners to compensate for declining national capabilities? Do international organizations increase or constrain the power and influence of their member states?

The answers the United Kingdom provides to these questions will shape its engagement with international politics in the years to come. A vote in favor of a British exit would embroil London and Brussels in months of bitter argument, heightening already disturbingly high levels of European parochialism. It would weaken not only the United Kingdom but also the EU, deprived of its most globally engaged and militarily powerful member state.

TIGHTENED PURSE STRINGS

Budget cuts are the most visible sign of the United Kingdom’s retreat. The budget of the Foreign Office has been cut by 20 percent since 2010, and the ministry has been told to prepare for further reductions of 25 to 40 percent. The armed forces have also been downsized, with the army alone expected to shrink from 102,000 soldiers in 2010 to 82,000 by 2020. The former head of the Royal Navy has spoken of “uncomfortable similarities” between the United Kingdom’s defenses now and those in the early 1930s.

The United Kingdom does not merely lack a grand strategy. It lacks any kind of clearly defined foreign policy at all

So much have British capabilities declined that during NATO’s 2011 mission in Libya, the United Kingdom was painfully dependent on U.S. support to fight a third-rate military. In the current campaign against the Islamic State, a shortage of already antiquated Tornado ground attack jets has kept the British contribution to the air strikes limited, with only eight aircraft being deployed. And the United Kingdom’s decision to scrap its Nimrod maritime surveillance aircraft in 2010 has left the country vulnerable to the incursion of Russian submarines in the Irish Sea.

The penchant for disengagement has not been confined to the executive branch. In 2013, the British Parliament voted against intervention in Syria, presaging a more cautious approach to military intervention in general. Public opinion seems equally allergic to foreign entanglements. A 2015 Pew poll found that less than half of the British public favors using force to defend the territory of a NATO ally that falls victim to armed aggression. It was hardly inaccurate for the foreign secretary, Philip Hammond, to declare, in the run-up to the 2015 election, that “there are no votes in defense.” Meanwhile, the opposition Labour Party has elected a leader, Jeremy Corbyn, who is opposed to all military intervention unless explicit UN approval is secured, who has compared atrocities committed by the Islamic State to U.S. actions in Fallujah, and who has called for British withdrawal from NATO.

FOLLOW THE MONEY

As British policymakers have lost interest in engaging with the outside world, they have embraced a shortsighted conception of economic interests. The Foreign Office has had its ambitions lowered, with its main role now to promote trade as part of the government’s so-called prosperity agenda.

This narrow focus can be seen most clearly in China, where the British government has pursued political appeasement for economic gain. In July, the United Kingdom initially refused to grant a visa to the Chinese dissident artist Ai Weiwei, which many saw as an attempt to curry favor with Chinese President Xi Jinping before his visit to London in October. Although most parts of the Foreign Office have faced severe cuts in staff, the British embassy in Beijing has become bloated with commercial employees.

Russian oligarchs seeking property in London continue to receive a warm welcome, despite their support for Russian President Vladimir Putin.

Observers could be forgiven for thinking that the notion that China may pose a geopolitical challenge has not occurred to the British foreign policy establishment. On his recent trip to Indonesia, Malaysia, Singapore, and Vietnam, Cameron said next to nothing about the security concerns troubling that region, but he did oversee the signing of several trade deals.

Such mercantilist priorities are also shaping British foreign policy in the Persian Gulf, where, for instance, the pursuit of lucrative arms contracts with Bahrain has come to supersede strategic considerations of regional stability or the promotion of democracy. A similar myopia defines the British response to Russia. Almost a decade since the former Russian spy Alexander Litvinenko was murdered in London, most likely by Russian agents, there is still no sign of a coherent British approach to Russian aggression beyond the occasional firm word. The United Kingdom has been content to leave it up to France and Germany to lead the European diplomatic response to the Ukrainian crisis. And Russian oligarchs seeking property in London continue to receive a warm welcome, despite their support for Russian President Vladimir Putin.

What is so confounding about London’s narrow mercantilism is that even if economic prosperity were the chief objective of foreign policy, the current approach would still be shortsighted. Profitable trade depends on the preservation of a stable and rule-bound international system, which both the Islamic State and Putin seek to revise. China may be a large and enticing market, but geopolitical rivalry in Asia represents a real threat to global prosperity. An emphasis on trade policy alone will do nothing to address major challenges to the international order, including piracy off the coast of Africa, the Islamic State’s attempts to throw the economies of the Middle East and North Africa into turmoil, and the massive flow of migrants across the Mediterranean. No European state—indeed, no state at all—can hope to confront these challenges alone. For a country with limited means, dealing with problems of this scale requires collective action.

IN OR OUT?

Yet precisely when international cooperation is needed most, a new political argument threatens to weaken the United Kingdom’s ability to collaborate: the debate over whether the country should leave the EU. Cameron has promised a referendum on EU membership by the end of 2017, and it appears likely that one will take place in 2016. The United Kingdom—like all EU members—continues to pursue its own foreign policy alongside those formulated for the EU as a whole in Brussels. If, however, it votes to leave the union, it will weaken its global influence and further jeopardize the stability of the international order.

For some proponents of a British exit from the EU, or “Brexit,” withdrawal forms part of a broader strategy of retrenchment. Twenty-four of the 30 Conservative members of Parliament who voted against intervention in Syria also defied their own party to vote in favor of a referendum on EU membership in October 2011.

For other Euroskeptics, however, a British exit offers a way of reinforcing the United Kingdom’s global heft. Nigel Farage, the leader of the right-wing UK Independence Party, has held out the vision of the United Kingdom outside the EU as a “thriving, energetic, global hub.”

The clunky, bureaucratic EU, these Euroskeptics argue, lacks the agility to pursue the kind of nimble foreign policy that a globalized world increasingly demands. Besides, they point out, the economic benefits of continued membership are small. Almost 60 percent of British exports currently go to countries outside the EU, so it makes little sense for so much of the British economy to be bound by the EU’s strict regulations. And for those worried about geopolitical challenges, a United Kingdom that left the EU would still have its security guaranteed by its membership in NATO.

Many of the criticisms of the EU as a forum for foreign policy collaboration are accurate. More than 20 years of trying to create what the EU terms a “common foreign and security policy” has led to countless summits, declarations, targets, and rhetoric, but precious little in the way of substantive policies. There is little meaningful European defense collaboration, nor is there a robust common policy toward China. And when it comes to confronting insecurity in its own backyard—whether to the south or the east—the EU has strategies aplenty but few effective policies.

Britain's Prime Minister David Cameron (L) meets with China's President Xi Jinping in The Hague, March, 2014. Yves Herman / Reuters

Yet the Euroskeptics are wrong to ascribe all the blame for these failings to the much-maligned bureaucrats in Brussels. A lot of the fault lies with the member states themselves, who have refused to commit themselves wholeheartedly to a multilateral European foreign policy. But since the capabilities of even large EU members, such as the United Kingdom, are declining, they have little choice but to invest in an imperfect institution.

Only the EU possesses structures to foster cooperation on everything from trade policy to sanctions to the defense industry. In a complex world, economic and security problems are intricately intertwined, and only a comprehensive approach to them has any chance of success. A more genuine commitment to such multilateralism from key member states, such as the United Kingdom, is essential to ensure that institutional inadequacies in Brussels are successfully addressed and overcome.

FORTRESS BRITAIN?

Buried within some of the Euroskeptics’ criticisms of EU membership lies a paradox about British power. On the one hand, advocates of Brexit argue that London is too weak to wield sufficient influence in Brussels. They contend that the EU’s ­excessive regulation and ­internal empire building—epitomized by its drive toward “an ever-closer union”—are long-term trends that the United Kingdom can do little or nothing to stymie. On the other hand, the skeptics maintain that the United Kingdom is so inherently powerful that free from the shackles of the EU, it would suddenly enjoy enough global heft to negotiate trade deals effectively with the likes of China.

The evidence suggests that, at least when it comes to China, London has limited influence. In May 2012, during his first term, Cameron met with the Dalai Lama, provoking Chinese criticism, before changing course and voicing opposition to Tibetan independence the following year. Yet neither move engendered any perceptible change in Chinese policy. Nor is there any credible evidence that London’s pandering to Beijing was the reason China invested twice as much in the United Kingdom between 2012 and 2014 as it had in the previous seven years.

A migrant stands along a security fence topped with barbed and razor wire near the makeshift camp called "The New Jungle" in Calais, France, September, 2015. Regis Duvignau / Reuters

Even if the United Kingdom were able to strike an advantageous trade deal with China by leaving the EU, it would be forgoing far more important benefits of EU membership. For one thing, trade is not merely about trade. The Transatlantic Trade and Investment Partnership, currently under negotiation between Brussels and Washington, could provide significant economic benefits (primarily from the removal of nontariff barriers, as tariffs between the United States and Europe are already low). Yet its implications are geopolitical as much as economic. The deal is as much about underlining the solidarity of the nations of the Western Hemisphere in the face of common political challenges as it is about eking out marginal gains from opening trade still further.

And this solidarity is crucial in today’s unstable world. The United Kingdom cannot defend its interests alone. Many proponents of Brexit argue that international collaboration should occur with the United States rather than through the EU. Yet it’s not clear that U.S. policymakers are interested in working with an insular United Kingdom adrift from the EU. British timidity feeds U.S. disenchantment with the United Kingdom by contributing to the perception that the country is disengaging not only from Europe but also from the wider world and that it is willing to sacrifice geopolitical principles in the name of prosperity. The United Kingdom’s absence from the Minsk talks over the crisis in Ukraine and from unstable regions such as the Sahel—precisely where the United States is looking to Europeans to pick up the slack as it pivots toward Asia—reinforces such doubts across the Atlantic.

Solidarity is crucial in today’s unstable world. The United Kingdom cannot defend its interests alone.

These days, Washington is longing for its allies to take on a greater share of the burden of maintaining security in their own backyards. Moreover, and in stark contrast to earlier periods, Washington has increasingly come to believe that for the Europeans to be able to maintain security, they will need to work together within the EU. No longer does Europe stand in opposition to the transatlantic relationship; it now represents one of its building blocks. The route to a more effective NATO runs through central Brussels. It is precisely by using EU structures that Europeans can best facilitate the military collaboration that is required to strengthen the transatlantic alliance.

A MORE PERFECT UNION

It is difficult to exaggerate the difference the United Kingdom could make if it decided to throw itself wholeheartedly into the work of building collective foreign and security policies. On the rare occasions when London opts for such engagement—as it has with the EU’s mission to combat piracy off the coast of Africa, for example—collective action proves enormously effective. But when it remains diffident about taking the lead in the EU, it not only weakens the EU but also creates a self-fulfilling prophecy: by contributing to the EU’s ineffectiveness, British reluctance to provide leadership serves only to strengthen the arguments for Brexit.

As one of Europe’s strongest military powers, the United Kingdom is well placed to lead. It was Tony Blair’s government that finally allowed the EU, tentatively, to begin to formulate its own defense policies. And it was subsequent British diffidence that contributed to those policies’ increasing ineffectiveness. By taking the lead when it comes to collaboration over weapons programs, by engaging fully in discussions over how to implement European military interventions, and by actively helping shape the union’s foreign policies, London could arguably do more than any of its partners to reinforce Europe’s international influence.

Uncertainty about the United Kingdom’s place in the world is hardly a new phenomenon. In 1962, former U.S. Secretary of State Dean Acheson declared, “Great Britain has lost an empire and has not yet found a role.” Today, the United Kingdom exhibits an even greater reluctance to engage in international affairs. The upcoming referendum will determine whether the country’s retreat will continue unchecked. Yet whether it wishes to or not, the United Kingdom cannot detach itself entirely from events in eastern Europe, the Middle East, or Asia. Collective European action, of precisely the kind the EU was designed to foster, represents the only viable alternative.