From 1859 to 1872, the 142sq km San Juan Island nearly pulled the United States and Great Britain into war.

San Juan is one of a welter of islands and islets off the northwestern corner of Washington state, itself in the northwestern corner of the US. It is cradled by a British Columbian archipelago; Canada reaches down and embraces Washington state. And that was the problem, before the border was definitively set.

San Juan is – well, not worthless, but its only real industries are farming and tourism. Barely more than 2,000 souls live there. But some 37 years after the War of 1812, it threatened to become a flashpoint that would renew American and British hostilities.

It was a classic case of escalat­ion, and it’s comedic in retrospect. An American squatter shot an Irishman’s pig on the British-held island. When authorities threated to arrest the squatter, local US settlers reacted with righteous indignat­ion, bolstered by loose cannons in the American military who wanted to embroil their country in war. Their goal was that, when the US Civil War finally began, Lincoln and the North – faced with two conflicts – would quickly surrender.

Both countries sent more and more troops. Diplomats, all of whom knew the stakes, laboured mightily to prevent “collision” (the word “war” was seldom if ever mentioned). However, Americans on the ground only made things worse. The matter was finally resolved thanks only to arbitration by Kaiser Wilhelm I.

Coleman, a former Royal Naval officer, presents a detailed, concise and fascinating study of the entire affair. He gets on wobbly ground, however, with his conclus­ions. He offers the Pig War as an early example of American imperialism, the first in a series of ever larger land-grabs, culmin­ating in World War I, which saw “America presented with a perfect opportun­ity to weaken British influence in the world.” Speaking as an American: Gee, sorry we interfered with your Great War when it was going so well.

More seriously, interpreting a foolish dispute as imperialism on the eve of Britain’s most expans­ionist period is the pot calling the kettle black. And it ruins Coleman’s thesis: It was indeed “the most perfect war”, and the conduct of those in power, who fought so valiantly to prevent “collision,” is a tribute to sanity. If only all heads were so cool and all warfare so civilised!