Try reading Article IV Section 4 for comprehension sometime:
The United States shall guarantee to every State in the Union a Republican form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.
(Emphasis supplied for the myopically impaired.)
What, did someone repeal Article I on us? Article I, Section 8: To provide for calling forth the militia to execute the laws of the union, suppress insurrections and repel invasions. Article IV, Section IV: "The United States shall guarantee to every state in this union a republican form of government, and shall protect each of them against invasion; and on application of the legislature, or of the executive (when the legislature cannot be convened) against domestic violence." Obviously the Southern states were in insurrection and opposing the execution of the laws of the Union. And considering that the state governments were the ringleaders then it is folly to think the President had to wait for them to call for their own suppression. But folly makes up so much of the Southron argument.