The referendum on whether the United Kingdom should remain a member of the European Union is a wake-up call for the single market of 28 nations and more than 500 million people. The fury over economic and political cooperation that led to the referendum won’t subside once the results are known and could, in fact, intensify. “The future of Europe, the transatlantic alliance and the international liberal order are all in play, and the June 23 referendum has done little to settle them,” writes Daniel Twining, director at the German Marshall Fund of the United States. He urges E.U. and global leaders to contemplate the disturbing trends for democracies—a backlash against globalization, fears about diversity and immigration, mistrust over trade agreements and uneven distribution of benefits, and fragmentation as nations withdraw from global challenges demanding cooperation. Twining suggests that rising populism and “domestic insurgencies will roil the ranks of the major powers, with potentially widespread strategic and economic consequences for the fragile international system.”

Security is essential for economic viability, and the terrorist attacks in Paris and Brussels suggest that European Union leaders underestimated the jihadist influences within their cities and the aggression near its borders. EU leaders must master geopolitics, influencing regional events, and engaging in great power competition. The continent may be over-reliant on the United States for security, writes Daniel Twining, director and senior fellow for Asia at the German Marshall Fund of the United States, adding that the European Union must adapt to new forces transforming global politics or risk the fate of previous imperial experiments to unite the continent, all of which ended in failure.” For a model Europe might consider parts of the U.S. response after the 9/11 attacks—increasing intelligence and military spending, consolidating and eliminating barriers among security agencies, increasing surveillance, developing domestic energy sources, and leveraging a network of allies.