After returning from the missile crisis, we were stationed at camp San Mateo, Camp Pendleton, CA. Liberty cards were still a must. Some thought the fire breaks were for fire and not travel, but we found them very useful for unauthorized entry.
While returning one night, we drove to the gate just south of Mateo and north of the border check point, where we entered the base on a fire break ... in my '56 Ford. After a short ride, we once again put one over on the liberty card thing ... well, ALMOST. In my rearview mirror, we saw those lights flashing. I stopped the car on one giant dust hill to see the Border Patrol with guns drawn and speaking to me in Spanish saying something about "illegal entry" into the U.S.
As you might imagine, it was a learning experience explaining to base security how grunts had made them look bad in the eyes of all concerned. Ah, just another day in the Corps!
Semper Fi!