"Be not afraid of greatness: some are born great, some achieve greatness and some have greatness thrust upon them". - (Quote Act II, Scene V). Twelfth Night, Shakespeare
I guess that is of some comfort. Most people, whether they be in a massive city-state or a tiny commune don't go out hunting reanimates and dodging citizens. There are cock-ups to be sure, but generally action only comes around if you ask for it. In turn, that means signing up for a citizen militia or similar organisation. City defense forces are as varied as the places they represent, I'll run you through a few.
Thieves and cowards with more self-preservation than respect for authority are the Bread and butter of the NEST RAT sandwich. It is strictly bring your own equipment and volunteer work, though some get "volunteered" to repay debts, if you catch my meaning. Rapid Access Technicians put resource recovery far above search and destroy and avoid direct combat when possible. Indirect combat via ambush and booby traps is a hobby for some of them, but the real defense of the arcology towers rests on the remnants of the national guard units stationed within.
New Birmingham's Citizen Militia is more of a police force than an army, and Right Though an ecclesiastical SWAT team. They all work together and have guns - but there is a big difference between breaking up a domestic disturbance and busting up a bunker. I wouldn't want to rob a bank down South - a conscript army is still an army you know - but most are chant bible verse first, shoot second. Heck, their ghouls are better trained than most of the Sheppard's Hand. You hear that right. Take everything you hate about Reanimates and most of what you dislike about being shot at, and you get the holy roller's secret weapon. Only come out for big trouble and only outside the city gates, but what defines "big" or "trouble" is kind of malleable.
If you truly want to be among the military, and the best it has to offer at that, you're looking for Crossbow - the US Government Special Forces Team. They're the ones who make sure that no one messes with old depots or missile silos while the government has its back turned. 'Course, if you're not already a navy SEAL who hiked out to Area 51 with nothing but a K-bar, chances are you won't make the grade. Rumor has it these guys have military cybernetics or other black project gear to aid them. The same has been said about Tesla's "Out Reach" force - but really, who is more likely to have that stuff - army commandos or trans-human geek nut-jobs?