> Following the declaration of secession by South Carolina on December 20, 1860, its authorities demanded that the U.S. Army abandon its facilities in Charleston Harbor. On December 26, Major Robert Anderson of the U.S. Army surreptitiously moved his small command from the vulnerable Fort Moultrie on Sullivan's Island to Fort Sumter, a substantial fortress built on an island controlling the entrance of Charleston Harbor. An attempt by U.S. President James Buchanan to reinforce and resupply Anderson using the unarmed merchant ship Star of the West failed when it was fired upon by shore batteries on January 9, 1861. South Carolina authorities then seized all Federal property in the Charleston area except for Fort Sumter.

To summarize: 1) South Carolina secedes. 2) South Carolina demands the Union remove its troops from their soil. 3) The Union refuses, garrisons a fortress on foreign soil, and attempts to resupply said garrison. 4) South Carolina offers an ultimatum--remove your soldiers or we will attack. 5) The union refuses to remove their troops from foreign soil. 6) South Carolina's militia attacks Ft. Sumter.

South Carolina's militia fired the first shots, but I'm not sure how you can say that they 'Initiated hostilities'. Occupying foreign soil has always been considered an act of war. History is written by the victors, I suppose.