The answer to your question is true :)
He found it necessary because Lincoln was only transferring food to the Northern army at the fort. However, once the ship came to the fort, it was believed (or assumed) by the south that inside the ship were supplies of weapons, soldiers, anything besides food. The South then opened fire, catching the North off guard and the first battle of the Civil war began.
Restructuring of the south, and allowing the southern states back in