France, led by the Emperor Napoleon III, had, if anything, been even more eager to intervene in the Civil War than was the case with Britain. But France was thoroughly bogged down in its plan to install Maximilian Habsburg of Austria as the new Emperor of Mexico.

Maximilian arrived in Mexico City in the summer of 1863 and established his reign, but it was obvious that he needed French troops to maintain it. The Mexican rebels—or nationalists, as they called themselves—meanwhile retreated to just south of the American border. They set up camp in what is now Ciudad Juárez, named for Benito Juárez, the first person of native blood to become president of Mexico.