The Rock of Gibraltar, as seen from La Linea de la Concepcion near the southern Spanish city of Algeciras. (Jorge Guerrero/AFP via Getty Images)

In the shadows of the massive rock pictured above live roughly 30,000 Britons, crowded onto a peninsula whose only land border is with Spain, and by extension, the European Union. Unsurprisingly, almost every single resident of Gibraltar, the United Kingdom's sole continental outpost, voted to remain in the European Union in the summer's referendum on “Brexit.”

Speaking to my colleague Griff Witte in January, Gibraltar's chief minister, Fabian Picardo, described the Brexit campaign's triumph as a moment of “deep sorrow,” as his constituents, in Witte's words, “are committed Europeans and because they knew the vote to leave would give Spain leverage.”

Leverage, in this case, regards heretofore weak Spanish claims on the territory. Despite its obvious geographical contiguity with Spain, and the fact that more than 12,000 workers commute into the territory from Spain every day, native Gibraltarians steadfastly maintain that they are British, as the land itself has been since the early 1700s. In a 2002 referendum, they almost unanimously reaffirmed that in the ballot box.

But with its essential reliance on the Spanish mainland, Britain's withdrawal from the open border and customs agreements of the European Union means that Spain can choose to exert crippling economic pressure as a bargaining chip.

On Friday, the European Union indicated that it would tacitly back Spain's claims on the territory in its draft negotiation guidelines for Brexit. The document stipulates that “no agreement between the EU and the United Kingdom may apply to the territory of Gibraltar without agreement between the Kingdom of Spain and the United Kingdom.” In other words, London will have to negotiate directly with Madrid on any Brexit-related arrangements affecting Gibraltar.

The wording was immediately lauded in Spain and seen as an affront in the U.K.

British Prime Minister Theresa May called Picardo on Sunday morning to say that the U.K. remained “steadfastly committed to our support for Gibraltar, its people and its economy,” and that she would defend the “freely and democratically expressed wishes” of its residents that had made their desire to remain part of Britain clear. A former leader of May's Conservative Party, Michael Howard, took the rhetoric up a few notches, saying that Britain would go to war against Spain for Gibraltar if necessary, just as Margaret Thatcher did against Argentina in 1982 over the Falkland Islands.

“Thirty-five years ago this week, another woman prime minister sent a task force halfway across the world to defend the freedom of another small group of British people against another Spanish-speaking country, and I’m absolutely certain that our current prime minister will show the same resolve in standing by the people of Gibraltar,” Howard told Sophy Ridge on Sunday on Sky News.

On Monday, British Prime Minister Theresa May laughed off questions about Howard's comments, while Spanish foreign minister Alfonso Dastis said he was “surprised by the tone of the comments coming out of Britain” and suggested some British politicians were “losing their cool.”

British politicians who did not support Brexit expressed alarm that “saber-rattling for war” against longtime European allies had begun even before negotiation guidelines had been agreed upon. “It is absolutely ludicrous and totally inflammatory,” said Tim Farron, leader of the Liberal Democrats.

Speaking to the BBC, former Labour party foreign secretary Jack Straw called any threats of military action against Spain “frankly absurd” on Monday.

In continental Europe, the escalation of the dispute over the weekend was perceived as bizarre and unnecessarily aggressive. “The warmongering rhetoric over Gibraltar is worrisome, though not so much for the actual prospect of a shooting war over those rocks, but rather what those comments reveal about the mind-set of those who are ready to elevate the narcissism of small differences to a causa belli,” said Cornelius Adebahr, a European affairs experts with the German Council on Foreign Relations. “All countries concerned are NATO allies, so the actual idea of going to war is insane.”

Adebahr cautioned that bigger E.U. members like Germany are not interested in an escalation of the dispute, and tend to disagree with Spain's basis for territorial claims.

Gibraltar is home to a British air base, airport and seaport, and it is only 12 miles from the coast of North Africa. The U.K. handles its security and foreign policy, while leaving all other matters, including taxation, to the local government.

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