We can do what antifa did and trigger a civil war by chasing out the government police from an area and declaring it an independent state, then we set up our own government there, don't mismanaged it into ruin like the commies did, fortify the borders, and immediately prepare for repelling a governmemt seige.
One things have settled, we care for our own, refortify the borders, and move out to expand the zone, fortifying each new land grab as we do so.
Run a functional independent state well enough and your government starts to appear legitimate in the eyes of those who live there.
The secret to good government is a scientific approach, obviously you start with national socialism, but call it something different and insist on the new terminology, test out different policies to see what works best and keep an eye out for what doesn't BEFORE it becomes a major problem, them implement policy changes and see how those work.
Keep optimizing your government over and over and it will appear as if you actually give a shit about making a system that works, rather than just getting off on imposing your preferred policies on everyone else.
You can expect a lot of people to try and enter your new state, you have to manage them wisely as well, these can be recruits to fight, workers to support, parents to grow your numbers.
They can also be saboteurs, rivals, and opportunists, vet the people who come in well, get someone to do it who is heartless in his adherance to the standards for immigrants, and can spot bullshit or a problem individual from a mile away. It will pay off to be paranoid
You will 8nspire similar seccession movements in other parts of your country, and in other countries across the planet, help them out if you can afford to, choose who to help and in what manner by how it impacts your own struggle, let's them know that this is your basis for deploying aid, and should be theirs as well.
Focus on indoctrination and brainwashing fir your people and prisoners, best thing to do with a captured enemy is to turn him into a friend who loves his captors, dont release him, but make sure he adapts to your ideology.
Establish your new state as one of science, one of freedom, one of security, and set up your enemy as the opposite, appeal to the ideals your people likely already think of as being positive, and make a case as to why your society better embodies these ideals better than the enemy.
Try to hit the common denominator first, then appeal to apply a personal approach to the sub-groupd within your population.
Remember that good propaganda is not manipulating the truth, but manipulation of how the truth is perceived and reacted to, introduce a self setving bias where everything is interpreted as "rebels good, establishment bad".
It's better to have a people who believes that you will keep them.from the things they fear, than to have them think you will give them what they desire. Most people are OK with being comfortable.
There are no rules in civil war, fighting dirty in order to take down a larger foe is a smart move, there is no shame in taking strategies and tactics from the enemy and turning them against their first wielders. It's essential, adapt, evolve, overcome. Always gave a new approach going on somewhere, keep the enemy guessing, unpredictability is the best asset, but not to the point of causing your own guys to be confused or abandoning a good standard operation procedure out of a pursuit of novelty, most of your fighting will be done by a formula.
As you are the defense fir the first half, you need to make the environment favor you, set up traps, lots of them, make most traps obvious and nonfunctional in order to lure the enemy into the well hidden and effective ones. Holes and tunneks are great fir positioning, going underground and attacking the enemy from behind when they are already in the middle of a fight, make the holes deadly to the enemy make lots of fake ones that these guys have to check, make a habit if keeping hostages down there so that they don't just fill up the holes as they go.
Like I said, rice fields tactics are gonna be your best bet. And different environments offer different types of opportunities to exploit.
The war is basically won when two independent zones expand to the point where they meet and merge, do this as much as you can as soon as you can.