Lincoln opened fire on them first by sending a war fleet with orders to use it’s entire force to put men and weapons into fort Sumter.
A lie which DiogenesLamp well knows but repeats endlessly anyway.
In fact, Lincoln's order to his commanders was the same as he directly told SC Governor Pickens: no first use of force.
Confederates fired first to seize Fort Sumter, resulting in six Union casualties (7%), two of whom died.
The Union seven percent casualty rate is equivalent, for example, to British losses at the Battle of Yorktown, 1781.