How is the election of Abraham Lincoln as U.S. president in 1860 connected to the Confederate attack on Fort Sumter on April 12-13, 1861?

Abraham Lincoln was elected in November 1860; by December, South Carolina would host a secession convention, thus becoming the first state in what would become the Confederate States of America. South Carolina slave owners and many others in the Deep South feared that Lincoln's election meant the end of slavery, even though Lincoln's political platform only mentioned stopping slavery where it had already existed. Before April 1861, the Lower South had already seceded. South Carolina seized Fort Moultrie as it was on what they regarded as their property, even though it was a federal military installation. In the waning days of the Buchanan presidency, he sent a ship to resupply another beleaguered garrison at Fort Sumter--the ship was fired upon by Confederate shore batteries. Lincoln therefore did nothing to relieve the fort but did not give the commander there, Major Robert Anderson, permission to surrender. Lincoln did not send ammunition to the fort but rather waited for the Confederacy to fire the first shots of the war, which it did on April 12, 1861.

After Abraham Lincoln was elected in early November of 1860, the Confederate states began to secede from the country. South Carolina was the first Confederate state to secede, in December of 1860. When this occurred, the federal troops that had been stationed in Charleston, South Carolina, evacuated from the city and relocated to Fort Sumter in Charleston Harbor. The federal troops regarded the fort as located on federal ground, but the Confederates claimed the fort as their own. After Lincoln assumed office in March of 1861, he was pressured to take some action about Fort Sumter, as the troops in the fort (who had been sent supplies by the previous President, Buchanan, in January of 1861), were running out of supplies. In early April, Lincoln decided to send supplies to the fort but said he would not send ammunition if the Confederacy did not attack. However, on April 12, 1861, the Confederacy fired on the fort, and the Civil War began.