Critiques of the idea of anarchist defense argue that the populace needs an organized standing army to protect its safety. (In fact, modern "strategists" argue that this army needs to invade the country’s enemies constantly, carrying the war to their shores, no matter how little effect and how much the blowback.)
They assume that if United States, for instance, were invaded, this is how the conflict between a defending anarchist army and attacking statist army would look:
But in reality, it would like something like the following, which is why, during his presidency, Thomas Jefferson argued that America needed no standing army to defend itself. If needed, an effective militia force could be quickly organized.
Of course, if you take away the people’s right to bear guns, no militia can be organized. The defense of the people remains in the hands of a monopoly that invades other countries and searches old ladies and little children in the airports but fails to defend against attacks on American soil despite multiple warning from the intelligence. The defense of private citizens from criminals (who do not obey gun-control laws) remains in the hands of inept police force.