The U.K.’s Next Prime Minister Will Face NATO’s Hardest Test

The U.K.’s Next Prime Minister Will Face NATO’s Hardest Test
Andy Burnham speaks to supporters after the Makerfield by-election in Ashton in Makerfield, England, Friday, June 19, 2026.(AP Photo by Jon Super)

As NATO leaders gather in Ankara this week, one of the people most likely to shape the alliance’s future is not in the room. Within weeks, Labour lawmaker Andy Burnham is expected to become the United Kingdom’s next prime minister, inheriting the political, fiscal and industrial challenge of turning NATO’s new ambitions for Europe into military capability.

Burnham, a self-identified socialist in the “soft left” tradition, is widely expected to continue outgoing Prime Minister Keir Starmer’s solid commitment to NATO. But London can’t do it alone. And across the English Channel, France is confronting a reckoning, as the far-right NATO-skeptical National Rally gains ground ahead of next year’s presidential election to decide who will succeed President Emmanuel Macron. The relationship between London and Paris, Europe’s two nuclear powers, could become the political center of the continent’s security architecture just as the ideological distance between their governments widens.

For all of Europe’s political complexity, no elected leader will sit closer to the junction between U.S. military power and European security than the U.K.’s next leader. As custodian of one of Europe’s two independent nuclear deterrents and Washington’s closest defense partner on the continent, whoever walks through the black door at No. 10 Downing Street will carry responsibilities that extend far beyond Britain’s shores.

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