Note the key word there, armistice.
Does not that word "armistice" imply a state of war preexisted Lincoln's inauguration, in which an informal "armistice" had prevented bloodshed?
And if a state of war pre-existed Lincoln's inauguration, who initiated that?
Who made surrender demands on Union forces in Union forts throughout the seceding states?
In what conceivable sense were such demands not in and of themselves acts of war?
The truth of this matter is that Lincoln in March-April 1861 only ordered what President Buchanan had previously done in January 1861 -- sent ships to resupply or reinforce Union troops in the two remaining Union forts, Sumter and Pickens.
The difference was that Buchanan's January resupply ship to Fort Sumter was fired on by secessionist forces, and so went home, mission not accomplished.
Lincoln's ships in April triggered Jefferson Davis to demand immediate surrender of Fort Sumter, and when Major Anderson temporarily refused, Davis launched a military assault which soon forced the surrender.
So Lincoln did nothing basically different from Buchanan, but Davis took the opportunity to start war, and soon after formally declare war on the United States.
In Lamp Boys fever swamp of a mind a war existed. Forget Bro Joe, Lamp Boy’s a loon.