Right wingers have organized militias for decades. These might be made up of stupid fat fucks, but they have trained how to organize, communicate, and do logistics.

The number and quality of weapons is one factor. Wars are won by logistics, communication, and coordination. If you have an existing social political network, you can arm it pretty quickly. A group that knows how to set up a music festival in the middle of nowhere, can learn how to run a military camp.