The costliest war—the Civil War—in U.S. history also presented the country with significant consequences in the international forum. While the leaders in Washington, D.C., and Richmond, Virginia, contemplated campaigns on a scale unprecedented in modern warfare, American rivals prepared to exploit the distractions created by civil war. As armies numbering hundreds of thousands endured battles that dwarfed Waterloo, the United States found its survival challenged by formidable powers outside its borders.
The internecine war between Liberals and Conservatives in Mexico left the door open for foreign intervention. Citing uncompensated losses for property destroyed during the civil strife and Mexico's refusal to pay its foreign debt, England, France, and Spain demanded satisfaction. All three powers agreed to a joint intervention in October 1861 and occupied the port of Veracruz three months later. While Mexican leaders were able to reach an agreement with England and Spain, the French remained to carve out a new part of their empire. For years, Napoleon III had eyed the Western Hemisphere, entertaining designs that would expand French imperial power and his prestige. To achieve this, he dispatched the Archduke Maximilian of Hapsburg (brother of the Austrian Emperor Franz Josef) to Mexico. 1
In the early stages of the war, few Europeans expected that the American union would survive. Although the industrial resources and the population base of the North appeared more than adequate to protect the remainder of the United States from a Confederate victory, significant doubts existed as to whether the Union could muster the means necessary to reunite the country. It was an open question whether it was possible for northern armies to prevail in a continent where the distance from Washington, D.C. to New Orleans was greater than that from Berlin to Moscow. 2
President Lincoln's most pressing diplomatic priority was to bide time adequate enough to stave off either foreign support of the Confederacy or open