The actual historical record shows five war ships plus three hired tug boats. The Baltic transported about 200 troops, and the Powhatan another 300 sailors, but neither landed at Fort Sumter.
Troop strength within Fort Sumter was effectively zero before Major Anderson moved there from nearby Fort Moultree on December 26, 1860 with around 100 troops.
Soon after, President Buchanan, who did not believe military force could be used to prevent Southern secession, sent a hired civilian ship Star of the West to Fort Sumter with supplies for Major Anderson.
The Southern forces then in Fort Moultree fired on the Star of the West and these were the first shots of the Civil War -- against an unarmed civilian ship attempting to supply Fort Sumter.
Of course, President "dough-face" Buchanan did nothing about it, but President Lincoln on April 6 notified South Carolina Governor Francis W. Pickens that:
"an attempt will be made to supply Fort Sumter with provisions only, and that if such attempt be not resisted, no effort to throw in men, arms, or ammunition will be made without further notice, [except] in case of an attack on the fort."
"In response, the Confederate cabinet, meeting in Montgomery, decided on April 9 to open fire on Fort Sumter in an attempt to force its surrender before the relief fleet arrived."
Point is this: the SIZE of the federal resupply force sent to Fort Sumter had nothing to do with it. The South had already fired on the unarmed civilian Star of the West sent by President Buchanan in January.
So, whether Lincoln had sent one ship or fifty wouldn't have mattered. The South was determined to prevent resupply of Fort Sumter, no matter what.
Bottom line: Beaureguard's firings on Fort Sumter on April 12 were not the first shots of the war. Firing on the Star of the West on January 9 were the first shots. And Lincoln in April was simply attempting to accomplish what Buchanan had failed at in January.
The South was committed to using military force against the North on January 9 -- just three weeks after South Carolina declared its secession, and in the face of a President Buchanan who declared he would use no military force to prevent secession.
The Southern forces then in Fort Moultree fired on the Star of the West and these were the first shots of the Civil War -- against an unarmed civilian ship attempting to supply Fort Sumter.
Where to begin? Let's start with the "unarmed" civilian ship. There were 200 armed troops on board the Star of the West hiding below decks so they wouldn't be seen. If was an expedition to reenforce Fort Sumter, not just resupply it. From Vol. I, Series I, page 131 of the Official Records (my emphasis below):
HEADQUARTERS OF THE ARMY,
New York, January 5, 1861.
Major T. H. HOLMES,
Eighth Infantry,
Superintendent Recruiting Service, Fort Columbus:
SIR: By direction of the General-in-Chief, you will detach this evening two hundred of the best-instructed men at Fort Columbus, by the steamship Star of the West, to re-enforce the garrison at Fort Sumter, South Carolina.
They will be furnished with arms, and, if possible, one hundred rounds of ammunition per man. Orders will be given to the proper officers of the staff department to furnish one hundred stand of spare arms and subsistence for three months.
The officers assigned to duty with the detachment are Lieuts. C. R. Woods, Ninth Infantry; W. A. Webb, Fifth Infantry; C. W. Thomas, First Infantry, and Asst. Surg. P. G. S. Ten Broeck, Medical Department, all of whom will report for duty to Major Anderson, commanding Fort Sumter.
Yours,
L. THOMAS.
Now for the "first shots of the war" claim of your post. Perhaps what you posted is just Yankee history. The day before the Star of the West entered South Carolina's territorial waters, US guard(s) fired at a group of locals trying to enter Fort Barrancas in Florida.
From Wikipeadia (I know, it's Wikipedia):
His decision to abandon Barrancas was hastened when, around midnight of January 8, 1861, his guards repelled a group of local men intending to take the fort. Some historians suggest that these were the first shots fired by United States forces in the Civil War.
But there is more than Wikipedia. From Guardians of the Gulf, subtitled Pensacola Fortifications 1698-1980, by James C and Irene S Coleman, page 39:
... Slemmer began to consolidate arms at Fort Barrancas, and on January 8 had moved part of his company from barracks into Fort Barrancas. ... About midnight on the eighth a group of men approached the fort and failing to answer when challenged, were fired upon by the guard. ... These were the first shots fired by Federals in the Civil War.
Nice little book. I bought it at Fort Pickens a few days ago.