This diligently researched monograph recounts the tragicomic episode of the Anglo-French intervention in the River Plate in the mid-1840s. The purpose of the British and the French action was to coerce the Argentine dictator Rosas into desisting from his military meddling in Uruguay, where he was supporting the “federalist” general Manuel Oribe in his protracted siege of Montevideo—“the new Troy,” as contemporary journalists called it.

The naval and military operations of the two great European powers were moderately swashbuckling (a blockade of Buenos Aires, the capture of Martín García Island, a naval-commercial foray up the Paraná River), but got them absolutely nowhere. Actually, the intervention was a glorious muddle from start to finish. As David McLean shows, the British foreign secretary who got it going, Lord Aberdeen, wished to backtrack almost immediately, but the slow-paced communications of that pretelegraph era allowed the British and French envoys, William Ouseley and Baron Deffaudis, to pursue far more aggressive actions than their governments really wanted—for awhile. Aberdeen (who enjoyed working with the French) and his better-known successor, Lord Palmerston (who did not), were determined to cut their losses. The humiliating climb down entailed three successive diplomatic approaches to Rosas, who won virtually all the concessions he demanded.

McLean’s handling of this story is coolly judicious. He bases his account mostly on British archival sources, disclaiming any ambition to cover the connections between the intervention and the shifting politics of the River Plate countries —and his grasp of the Argentine and Uruguayan setting is occasionally a trifle wobbly. It is strange to see the mighty Paraná and Uruguay rivers described as “tributaries” of the River Plate, which is not a river but a bay, though admittedly a long one; he calls the Argentine provinces “states” and archaically refers to Asunción, Paraguay, as “Assumption.” (This was presumably how it figured in British dispatches at the time, but no English speaker calls it that now, and not many did then.)

These are small blemishes in an otherwise very competent (and enjoyable) narrative. McLean obviously intends his book to test the idea of “informal empire,” which the British are popularly supposed to have exercised in Latin America, and he demonstrates clearly that the idea is fairly vacuous when applied to the River Plate in the 1840s. The intervention was motivated more by politics (the protection of Uruguayan independence) than by overarching commercial aims. The Foreign Office never really liked traders very much. It made no effort to press commercial demands when the time came to disentangle Britain from what Palmerston, with characteristic breeziness, called “the Plata scrape.” His remains the best description.