Form militias, develop a culture similar to American Minutemen. Set up a system for gathering and disseminating information. A unified command. Flares and rapid response militias on standby. Become radiofags.

You are about 4.6 million people. Militarized that is enough, even if outnumbered 10 to 1.

Start building guest barracks if you have land to do it. You might have to quarter militias in the coming years.