Re: How much do you really need?
Yes it is. But it's also reality. The Japanese learned that on Okinawa. Read Che' Guevera's book, and others. Be invisible. Avoid any encounters with whoever might be an "enemy".
There was a Marine on Wake Island that survived with the clothes on his back for 3 weeks after the Japanese had secured the island. Wake is very small. He did it by hiding in the sand, and making sure nobody knew he existed. He ate what he could find or steal. Finally surrendered and was hanged.