Why Democrats Would Lose the Second Civil War, Too. If you want logical map of what would probably happen Kurt Schlichter was a Colonel in the Army and a graduate of the US War College. This is a good read.
A red counter-insurgency avoids the problem of a decentralized insurgency and insecure logistical lines. In the case of California, whose secessionist antics are approaching the point where President Trump could legitimately employ his power to crush insurrections, the tactical problem is relatively simple. For example, San Francisco is a hotbed of treason, but the populace is largely unarmed and is trapped in a confined area. You put a brigade on securing the Golden Gate and Bay Bridges, then put a brigade on the San Francisco Peninsula to cut off the I-280 and US-101 corridors. Next you go to the Crystal Springs Dam and cut off the water. Then you watch and wait as the tech hipsters run out of artisanal sushi rice and kombucha.