The fifth step to survive an invasion is to fight back, if no one fights back the country will be taken in a matter of weeks. The best way to fight against a conventional army which are used in full scale invasions is guerrilla warfare. We've seen this tactics used against massive conventional American forces in Vietnam and Afghanistan, its been proven time and time again that fighting against guerrilla warfare is like fighting against ghosts. The key to guerrilla warfare is to attack with strong and fast ambushes, and then run away before they can strike back.