Ocampo and the U.S. representative Robert Milligan McLane, giving their names to the McLane-Ocampo Treaty. The U.S. Senate failed to ratify the treaty. Had it passed, Mexico would have made significant concessions to the U.S. in exchange for cash desperately needed by the liberal Mexican government. 1860s In 1861, Mexican conservatives looked to French leader Napoleon III to abolish the Republic led by liberal President Benito Juárez. France favored the secessionist Southern states that formed the Confederate States of America in the American Civil War, but did not accord it diplomatic recognition. The French expected that a Confederate victory would facilitate French economic dominance in Mexico. Realizing the U.S. government could not intervene in Mexico, France invaded Mexico and installed an Austrian prince Maximilian I of Mexico as the puppet ruler of a Second Mexican Empire in 1864. Owing to the shared convictions of the democratically elected government of Juárez and U.S. President Lincoln, Matías Romero, Juárez's minister to Washington, mobilized support in the U.S. Congress and the U.S. protested France's violation of the Monroe Doctrine. Once the American Civil War came to a close in April 1865, the U.S. allowed supporters of Juárez to openly purchase weapons and ammunition and issued stronger warnings to Paris. Napoleon III ultimately withdrew his army in disgrace, and Emperor Maximilian, who remained in Mexico even when given the choice of exile, was executed by the Mexican government in 1867. The support that the U.S. had accorded the liberal government of Juárez, by refusing to recognize the government of Maximilian and then by supplying arms to liberal forces, helped improve the U.S.–Mexican relationship. At war's end numerous Confederates fled to exile in Mexico. Many eventually returned to the U.S. The Porfiriato (1876–1910) With general Porfirio Díaz's seizure of the presidency in 1876, relations between Mexico and foreign powers, including the United States changed. It became more welcoming to foreign investment in order to reap economic gain, but it would not relinquish its political sovereignty. Díaz's regime aimed to implement "order and progress," which reassured foreign investors that their enterprises could flourish. Díaz was a nationalist and a military hero who had fought ably against the French Intervention (1862–67). The U.S. had aided the liberal government of Benito Juárez by not recognizing the French invaders and the puppet emperor that Mexican conservatives invited to rule over them, and the U.S. had also provided arms to