No- they are not defenseless. You’re never far from a rifle. There are armories everywhere.
Every company (120 soldiers) has an armory.
When some one is shooting at you ... first thought “I must get to the closest armory” ...??????? It is like you on the street and you are being shot at ... and DAMN my weapon is down the block in my vehicle!
Technically, yes, but not evey unit is a combat arms unit and not every armory has weapons in it. The weapons that are on base are harder to get to than the crown jewels.