It takes two sides to start a war.
What the north wanted was for the laws to be obeyed. Lincoln even urged that the Fugitive Slave Act be obeyed.
Notherners -wouldn't- allow the government to be thrown down by traitors. That was clearly the motivation of the northern soldiers - and Lincoln also.
Notherners in 1861 gave what Dr. McPherson called "an eagle-scream of patriotic fury."
And the war came.
Walt