As years of Brexit drama end with the United Kingdom’s departure from the European Union, it is worth reflecting on the populist-nationalist upsurge there and elsewhere that has rocked the international establishment over the past decade. From rural England to Catalonia to the Arab Spring to the Rust Belt, diverse polities have come together to challenge established practices and norms of governance in ways not seen in generations.

Over half a century ago, the world saw similar upheavals in the waves of Asian, African, Middle Eastern and Caribbean decolonization that quadrupled the membership of the United Nations within a generation after 1945. Most of the new members were the “single-unit” nation-states we know today — Senegal, Kenya, India and others that inherited most or all of their borders from imperial maps.

But in a largely forgotten part of the story, the “federal moment” in postwar global history, according to historian Michael Collins, saw nearly a dozen federated entities proposed or attempted between 1945 and 1970. These experiments grouped together colonial units into larger, multiethnic federations. Most — the West Indies Federation, the Central African Federation and Malaysia, for example — were vehicles for decolonization. Others, such as the United Arab Republic and the “beta version” of the European Union, were the initiative of already independent states.

For their numerous champions in the global North and South, federations were the wave of the future. In less grandiose terms, they were seen as the surest path to postcolonial state and economic viability, especially for smaller, poorer and more isolated places whose prospects after decolonization seemed dire. But in almost all cases, their demise resulted from a version of the populist-nationalist surge familiar to us today: local, identity-driven popular resistance to distant, cosmopolitan-elite political projects. The disconnect can be fatal to such top-down designs.

The impetus to federate had several motives. Departing European officials saw in the federal model a way to preserve metropolitan influence after decolonization, by leaving in place economic, security and cultural links both between former colonies and with the former metropole.

Anti-colonial nationalists fighting for independence saw federation as a means to construct stable polities and viable economies capable of overcoming the poverty and underdevelopment bequeathed by colonial rule. Federation would create a cooperative apparatus for the state-directed planning seen as necessary to jump-start the “modernization” of postcolonial economies.

Some nationalists perceived symbolic as well as practical benefits. In the late French empire, actors such as Aimé Césaire, a writer from Martinique, and Léopold Senghor, the first president of Senegal, envisioned a radical remaking of “liberté, égalité, fraternité.” This enlarged and redefined French-speaking polity would live under one of several proposed federated models, reorganizing citizenship and governance and keeping its former colonies connected to France. For others, such as Kwame Nkrumah in Ghana or Gamal Abdel Nasser of Egypt, the symbolism was world-historical. They viewed federal experiments as having the power to erase the lines that the imperial era had artificially drawn across the Pan-African and Pan-Arab “nations,” as the cooperative fusion of former colonies would demonstrate their solidarity in independence.

The Cold War superpowers, for their part, remained wary of any federation scheme that might produce a setback in the bipolar clash, but they were vaguely supportive of most such designs. And so it seemed, federations promised something for almost everyone. Yet their promise proved short-lived, with most collapsing sooner or later, peacefully or bloodily. What they had in common was that, in virtually all cases, insularity and identity trumped solidarity and cooperation as local non-elites rebelled against the elites who favored federations.

For example, the West Indies Federation was launched in 1958 as the vehicle for decolonization of most of the British Caribbean. It was meant to achieve full sovereignty within a decade: 10 islands under one flag.

But crosscutting rivalries complicated internal relations from the start. During the Jamaican referendum of September 1961, a popular majority of islanders voted to leave the union — voting, in effect, that they were Jamaicans first and “West Indians” second. Despite the entreaties of leaders like Trinidad’s Eric Williams, who captured the zeitgeist among many elites when he declared “the entire world will federate or die!” popular opinion stubbornly resisted. Trinidad soon followed Jamaica out, and the West Indies Federation dissolved into smaller independent nations.

A similar story unfolded in Southeast Asia. The Malaysia of today is not the one intended by its British and Asian sponsors during the federal moment. That map added Singapore along with Borneo’s Sarawak and Sabah to “Greater Malaysia,” in hopes of ensuring a stable politico-ethnic balance among Malays, Chinese and Indians and forming the basis for a viable shared economy. Yet tensions that dated back to the wartime Japanese occupation and the postwar Malayan Emergency fueled division rather than solidarity. Explosions of street violence, primarily between Malays and Chinese fearing for their communal futures under the federation constitution, destabilized and doomed the union. In the end, Singapore departed for an uncertain future alone only two years after joining the expanded federation.

The story echoed in most of the other attempted unions of the federal moment in Africa and the Middle East. The exception to this failure of the federations was the early version of the European Union. The E.U.’s durability stemmed in part from its slower, piecemeal process of integration, reversing the sequence of the other 1950s federations. Rather than prioritizing political integration as a means to economic cooperation, the then-European Economic Community first reorganized trade and economic arrangements long before attempting any meaningful political fusion — an understandable approach, given the herculean task of rebuilding the European economy after the war.

Yet Brexit suggests that the E.U. has fallen victim to the same divisions that undermined earlier federations. Non-elite popular resistance to such projects finds expression in populist-nationalist identity politics.

The mid-century experiments in federation might seem far removed from Britain in the age of Brexit, but their underlying dynamics have much in common. They point to the ongoing challenges of citizenship, representation, identity, accountable governance — and crucially, to the flaws of projects that lack sufficient buy-in from non-elite members of a shared polity.

Accommodating all parties within a sustainable federal structure, one capable of sharing governance and protecting pluralism and equality, is a daunting challenge in the best of circumstances. Finding our way to doing so in the present day will require creative reimagining and attention to what the federations’ rise and fall foretold about many of the conflicts shaking and shaping our own time.