French troops captured Mexico City in June of 1863. The occupiers then convened an assembly of notables, composed of Mexican conservatives who despised the republic and its liberal Indian president, Benito Juárez, now leading a guerrilla resistance. This assembly, in April of 1864, named Maximilian Emperor of Mexico, so the fait was accompli . It offers a good example of generalization number three: Invaders can always find local collaborators who will accept their rule in preference to that of hated domestic rivals.

What was the United States doing all this time? The obvious answer is fighting the Civil War, which explains its inaction. Except that it was not exactly inaction. Napoleon’s Mexican foray became the problem of Secretary of State William H. Seward, a uniquely gifted former New York governor and U.S. senator and one of the nation’s best foreign ministers.

Like most Yankees, Seward was not so much interested in Mexico’s independence as in the exclusive right of Washington to interfere with it. In 1861, in fact, he endorsed a plan for the United States to lend money to Mexico to pay off the Europeans, secured by a mortgage on four Mexican provinces. He told European governments not to worry about the possibility of American foreclosure. “The United States are,” he wrote—note the plural verb—“the only safe guardians of the independence and true civilization on this continent.” But the deal was not accepted, and Seward then had to fjnd a way to defend the Monroe Doctrine against the French. And the Doctrine, however sacred in American politics, had no international standing beyond Lincoln and Seward’s power to enforce it, which was drastically limited by the Union’s ongoing military disasters.

Therefore, Seward, with gorgeous flexibility, changed strategies and tactics. Mexican sovereignty would be officially cherished and Juárez’s government-in-exile recognized. Seward informed Paris repeatedly that the United States would not tolerate the establishment of either a nonrepublican or a foreign-dominated government in Mexico, much less one that was both.

Yet he did so in a way that did not confront the French with military threats. Seward’s notes unswervingly insisted that Maximilian was not Mexico’s lawful ruler in American eyes, but they neither denounced Napoleon nor hinted at doing him any harm. “If we have war with France,” ran one, “it must be a war of her own asking. … We shall attack nobody.” Another suggested that sooner or later the French would, on their own, do the right thing: “I remain … of the opinion that … the future of Mexico is neither an immediate, nor even a vital question for either the United States or France … and therefore time and reason may be allowed their due influence on its settlement.”

Seward knew that the question was in reality vital for his own country, but as he wrote to one of his junior officials while the Wilderness campaign was raging, “This is not the most suitable time we could choose for offering menaces to

the Emperor of France.”

Seward did not enjoy universal support for his soft-spoken persistence. Here, generalization number four comes into play. Makers of public opinion who do not have responsibility for the results are often ahead of policymakers in demands for tough talk. The New York Tribune wanted action taken against Napoleon, whom it called a “perjured villain.” To the editor of the New York Post, matters were very simple. “Trifling will drift us into war. Let Mr. Seward tell Napoleon to get out of Mexico. That is all we need. As easy as that.”

Congress, too, liked to take a hand. In April of 1864, the House, by a vote of 109 to 0, resolved that it was “unwilling by silence to leave the nations of the world under the impression that they are indifferent spectators of the deplorable events now transpiring in the republic of Mexico.” Then, too, there were military leaders looking for fresh opportunities as the Civil War finally ended. Grant sent 50,000 men to the Mexican border in the summer of 1865, and there was even talk of raising a force of Union and Confederate veterans, placing it under the command of General John M. Schofield, and offering its services to Juárez.

By then, with the North victorious, Seward had a free hand to get tougher, but he did so on his terms. He diverted Schofield from the military assignment by asking the veteran of Sherman’s Georgia campaign to go to Paris as a special emissary, with these instructions: “I want you to get your legs under Napoleon’s mahogany and tell him he must get out of Mexico.” The message was unmistakable, but sounded better from a soldier seated at the negotiating table rather than in the saddle. In the same way, a Seward message of February 1866 was clear in its intent: “We shall be gratified when the Emperor shall give to us … definite information of the time when French military operations may be expected to cease in Mexico.” Gratified, indeed! Yet this bland request for information about a presumed certainty offered France a more graceful exit than a blunt “Get out or else!”

And Napoleon took the opportunity. Two months later, he announced his decision to withdraw his troops over a year-and-a-half period. His reasons have a certain contemporary resonance. By then, he had poured nearly 275 million francs into the operation, and Mexico was not yet secured. Generalization number five, then: Empires do not come cheap. There were better opportunities at the time for lowbudget conquest in Africa and Indochina—but only, as events were to show, in the short run!

With the French gone, Maximilian’s empire collapsed. He elected to stay gallantly with his people in Mexico City, where he was captured and executed by Juárez’s men in June of 1867.

An American newspaper mused: “If anybody deserves to be shot it is Louis Napoleon. He is the chief criminal.” He did, in the end, get his comeuppance three years later, when the Prussians defeated and captured him and the Parisians back home rose up and declared the empire at an end.

It was a happy-ending victory for Seward, and probably something of a relief, for there is no certainty that the Americans themselves were eager for post-Appomattox bloodshed. Dexter Perkins, the Monroe Doctrine’s leading historian, speculates that in 1865 most Americans wanted the Doctrine upheld “without necessarily wanting war; but one wonders what their choice would have been if they could not have one without the other.”

Thanks in good measure to Seward, they did get the one without the other on that occasion. I’d be the first to warn against simple-minded comparisons and obvious lessons. Yet I hope that this account has provided food for enlightened reflection, of which, whenever war is imminent, there cannot be too much.