How would a state start a civil war?

Let’s say that a number of American states declared secession from the U.S. and hostilities break out. How would the seceding states actually gain control over the military forces? I assume the state National Guard would be the main component of such forces, but how would the state (the governor?) actually go about this?

He’d issue orders - whether the troops followed those orders would be the big problem. Some would, many wouldn’t.

Well during the Civil War the seceding states called out their militias and seized Federal property (including army installations). The federal government offered little resistance until Fort Sumter partly due to incredibly small forces available (only sixteen thousand troops, mostly west of the Mississippi) and partly due to President Buchanan’s belief he should not resist secession with force. Neither of those circumstances would apply today.

That’s why I had to laugh when our dumbass governor said that Texas should secede. Right smack in the middle of the state is the largest military installation in the ENTIRE WORLD! So, upon declaration of secession, the Texas militia would simultaneously have to prevent the US military from entering the state, and from getting out.