As Britain detaches itself from the EU and nationalism is resurgent across the continent, realism requires that we challenge a cherished but hubristic myth about this supranational construct — namely that the grand European plan has kept conflict at bay for decades.

Granted, the original strategy of the EU’s founding fathers whereby they sought to enmesh the nation state in a network of economic relations to help secure peace by stealth was successful in bringing increased co-operation between formerly hostile states. The aim, in the celebrated phrase of French foreign minister Robert Schuman, was to make war “not only unthinkable but materially impossible”.

Yet stealth came at a cost. It has bred in the European political elite a habit of profound disrespect for public opinion and democratic process, not least in relation to referendums that yield the “wrong” result. That is an important component of the resentment behind the rise of rightwing populist parties in the EU. And the underlying claim that economic interdependence within, first, the Schuman-inspired Franco-German coal and steel community in the 1950s, and then the wider EU, has purged Europe of its ancient enmities is not only fanciful but based on a misunderstanding of the relationship between economics and national security.

The idea of trade as conducive to peace goes back at least as far as the 18th century French political theorist Montesquieu who argued in De L’Esprit Des Lois that the desire for financial gain could restrain the destructive passions that are innate in human nature. The thought resonated across the channel and morphed into the liberal internationalism championed in the 19th century by the English free trader and anti-imperialist Richard Cobden. Its high tide came with the publication in 1910 of The Great Illusion by Norman Angell, a British politician who argued that the economic costs of victory in war always outweighed the gains. Many took his thesis to mean that war was futile and thus no longer likely. Disillusionment followed in 1914.

The notion that economic interdependence curbs military aggression has nonetheless proved resilient. As well as inspiring the founding fathers of the EU, it features in the official pronouncements of the World Trade Organisation. Many academics, including the Nobel-winning Yale economist Robert Shiller, are firm believers. And indeed there are elements of truth in the thesis. Economic interdependence undoubtedly raises the economic cost of conflict.

Yet other factors provide a better explanation of the postwar peace. In the dangerous nuclear context of the immediate postwar period the existence of a common enemy during the Cold War was helpful in bringing France and Germany together. The taming of interstate rivalries was also facilitated by the US military umbrella. Above all, Germany, having suffered appalling defeats in successive world wars, understandably had no wish for a third self-inflicted catastrophe. Within the EU as a whole the appetite for conflict has been seriously diminished for the foreseeable future. For the populist parties, today’s enemies are globalisation, immigration, Brussels and any other perceived threat to national identity.

In the harsh world outside the EU, there is little to suggest that economic interdependence is a potent restraint on military aggression — witness Russian interventions in Crimea and eastern Ukraine. Once again nationalism trumps economic interest.

The more subtle interaction between politics and economics in the EU relates to the eurozone. Here economic interdependence is proving a recipe for increasing friction. In effect, Europe’s old balance of power politics has been internalised within an unstable monetary union, but with the difference that Germany has emerged as the hegemon, insisting on austerity through the eurozone crisis and running record current account surpluses. In the absence of a proper infrastructure — common fiscal policy, full banking union, mutualisation of debt obligations — the single currency has become a mechanism for generating endemic imbalances.

This chimes less well with the thinking of Cobden than of John Maynard Keynes, who argued in a Dublin lecture in 1933 that free trade combined with international capital mobility was a recipe for “strains and enmities”.

Since its foundation the EU has undeniably achieved much. But the notion that it has been the main force for peace and stability in postwar Europe has been wildly oversold, and intensified economic interdependence through monetary union has now become a recipe for political and economic turbulence. As the political elite contemplates the rise of rightwing populism it should not forget how often in European history identity has triumphed over interest. War between European member states remains unthinkable for the non-mythic reasons mentioned earlier. A retreat into damaging protectionism is another matter.