The secession convention meeting in Charleston, South Carolina occurs on December 20, 1860. Confederate troops fired on Fort Sumter on April 12, 1861. Let's see that's 3.5 months later. And for 3 of those 3.5 months the US has a lame-duck President in James Buchanan whose cabinet was also famously split oh the issue. Lincoln isn't inaugurated until March 4, 1861. Further, the attack on Fort Sumter is just the "official" start of the war. It's not like nothing was being done by the Union in the interim. Far from it. As early as January 5th of 1861 hundreds of troops and provisions were sent to fortify the Sumter garrison. Lastly on April 4th Lincoln tells his southern delegates that he intends to attempt to resupply Fort Sumter. This is understood by the Southern states to be a declaration of war. So yes I think this is exactly the example I portray it to be.