Well, the south didn't get the memo apparently. The role of the president was to preserve the union. Extraordinary circumstances called for extraordinary measures based on that objective.
The Declaration calls for "patient sufferance" to the point of losing what is yours. Curiously enough, it calls for that after it declares life an inalienable right for all people. The south didn't have the right to secede from the union for "light and transient" causes. It had to live up to its end of the Constitutional bargain. Lincoln defended the Constitution which was his duty.
You think economic sabotage is "light and transient"?
Because that is what the north was doing to the south. They put punitive taxes on the south and were driving them into poverty.
And do you really think that if you voluntarily join a group, that you may not voluntarily leave?
The General Assembly of each state ratified the Constitution and therefore joined the union. Why can they later not leave to union if the Assembly votes to do so?
But when a long train of abuses and usurpations, pursuing invariably the same object evinces a design to reduce them under absolute despotism, it is their right, it is their duty, to throw off such government, and to provide new guards for their future security
I call what the north was doing to the south "abuse" and "despotism". And per the Declaration, it was their DUTY to change it.
Lincoln was wrong. He had no authority to "preserve the union".
I suppose that once the south HAD seceded, they would technically be a separate country and he could ask Congress for a declaration of war against them.
But ONLY Congress can declare war. That is not the power of the executive branch. In any way whatsoever.
CONGRESS is the representative of the people. The power to wage war resides IN THE PEOPLE. THEY are the ones that will bear the cost in blood and treasure.
If the executive can wage war, what makes the president any different than say Napoleon or King George?
Executive wars are wars to bring glory and treasure to the executive, not for the good of the people.