From the Official Records:
March 28, 1861, the US Congress adjourned.
March 29, 1861
To the Secretary of the Navy
I desire that an expedition, to move by sea be go ready to sail as early as the 6th of April next, the whole according to memorandum attached: and that you co-operate with the Secretary of War for that object.
Signed: Abraham Lincoln
The memorandum attached called for:
From the Navy, three ships of war, the Pocahontas, the Pawnee and the Harriet Lane; and 300 seamen, and one month's stores.
From the War Department, 200 men, ready to leave garrison; and one year's stores.
April 1, 1861 by General Scott
April 2, 1861 approved by Abraham Lincoln
To: Brevet Colonel Harvey Brown, U.S. Army
You have been designated to take command of an expedition to reinforce and hold Fort Pickens in the harbor of Pensacola. You will proceed to New York where steam transportation for four companies will be engaged; — and putting on board such supplies as you can ship without delay proceed at once to your destination. The object and destination of this expedition will be communicated to no one to whom it is not already known. Signed: Winfield Scott
Signed approved: Abraham Lincoln
April 4, 1861
To: Lieut. Col. H.L. Scott, Aide de Camp
This will be handed to you by Captain G.V. Fox, an ex-officer of the Navy. He is charged by authority here, with the command of an expedition (under cover of certain ships of war) whose object is, to reinforce Fort Sumter.
To embark with Captain Fox, you will cause a detachment of recruits, say about 200, to be immediately organized at fort Columbus, with competent number of officers, arms, ammunition, and subsistence, with other necessaries needed for the augmented garrison at Fort Sumter.
Signed: Winfield Scott
All well and good. The Fox plan to resupply the Fort consisted of a string of boats being towed by a steam powered tugs past several Confederate batteries to land provision at the fort. Hardly an all out assault on the Confederate defenses of Charleston.
That order is dated April 4, signed by General Scott.
Those were Lincoln's final orders to Fox, whose resupply mission sailed on April 10.
So the decision to use Lincoln's resupply mission as the excuse to launch military assault on Fort Sumter (April 12), and war on the United States rested squarely with Jefferson Davis.