The Lincoln administration’s interests in Mexico in the spring of 1861 revolved around related three main concerns. First, the government under Benito Juarez needed to fully consolidate its power and eliminate the remaining vestiges of the recent civil war. Second, it was imperative that the Confederate states be unable to use Mexico to win their independence from the Union. Third, the Lincoln administration did not want European powers to take advantage of the civil war in the United States to interfere in Mexico.
On April 6, 1861, Secretary of State William Seward sent a message to Thomas Corwin, the former Secretary of the Treasury under President Millard Fillmore and the minister to Mexico under President Abraham Lincoln, outlining general and specific instructions for Corwin.
Seward mentions several grievances of the United States and its citizens against Mexico, including the murder of a US government official and complaints by US citizens that arose during the civil war in Mexico. Seward instructs Corwin to allow Juarez to “cement its authority and reduce the yet disturbed elements in society” before bringing up these issues directly. (65)
Unsurprisingly, the recent “difficulties” arising from the session of the southern states plays a central role in Seward’s letter. Seward tells Corwin not to “engage in any discussion of the merits of those difficulties in the presence of foreign powers, much less to invoke even their censure against those of our fellow-citizens who have arrayed themselves in opposition to its authority.” (66)
Rather, Corwin is to “assure the government of Mexico that … the President confidently believes and expects that the people of the United States … will speedily and in a constitutional way adopt all necessary remedies for the restoration of the public peace and the preservation of the federal Union.” (66)