Controlled Fermentation has been around for about 9000 years. The results of controlled fermentation is beer, wine, and spirits, bread, preserved fish and pickled vegetables. The importance of Fermentation in a survival situation can not be understated. If the situation that exist results in a long term absence of commercial food chain access, then your ability to harvest and preserve natural foods will be paramount to your survival.
If you had one thing that you could store in preparation for a long term food shortage, that one thing should be salt. Non iodized pickling salt would be my choice. It does not spoil and can be kept at any temperature or humidity level. It is essential in preserving meats, fish and vegetables. Meat, fish and vegetables can be found almost anywhere if you understand the edibility of wild plants and knew how to hunt and fish. Salt on the other hand, is only available in limited areas naturally. That’s why there were literally salt wars fought in Ohio. Ohio has a large salt deposit and that salt was essential to the survival of Native Americans and Settlers alike.
Fermenting vegetables is a very easy process. You basically need 4 things. 
Edible vegetables, clean non chlorinated water, salt and a vessel to hold it all. There are numerous YouTube videos on how to ferment, so I won’t get into the process in detail here. The basics of it is simple. Good bacteria thrive in relative saline solution that is void of free oxygen. 
The process of the bacteria feeding on the sugars in the vegetable provides a byproduct-Lactic Acid (which is why this process is known as Lactose Fermentation). The Lactic Acid is also hostile to harmful bacteria. The result is a saline-lactic acid environment that promotes the growth of healthy bacteria and prevents the growth of harmful bacteria.
To read more about the Science behind it without getting too crazy, click here.
There are some draw backs on pickling and that is storage. If you are on the move, it is tough to carry vessels of pickled vegetables. Hopefully however, you will find a place to settle down for extended periods of time. Hopefully you also carried as much salt as you could. Note: Fermentation can take place without the salt, but it may not be as safe a product.
The positives of fermentation are so tremendous that you should consider fermenting even when not in a survival situation. 
The benefit to your gut that the good bacteria (they are probiotic in nature) provides is tremendous. The bacteria breaks down the cellulose and allows your body to better digest and make use of the available nutrients. The nutrients tend to increase in the process rather than decrease. The vegetable matter provides fiber that is easily processed, resulting in easier digestion. Here is a fantastic benefit. 
The end product taste way better than what you can buy at the store. Almost not comparable. The store bought is pasteurized and is basically dead. Fermented is alive and will help you stay alive as well.
