With food and water, we can ensure that we are not hungry when we can't cook and eat normally, that we won't starve to death because of lack of food, that we have enough energy to fight and escape from war and gunfire, and that we can have drinking water and food supplements to maintain the life and metabolism of the new city.
If war is coming, rich people can exchange real estate, deposits, bonds, jewelry, antiques, paper money, etc. for gold, which generally depreciates less and is more valuable than money.
Extended data
War will make the currency depreciate rapidly, and people's transactions on the black market are just one thing for another. The black market exists because of people's needs, so what the black market lacks most is food, but what it lacks most is wine. First, alcohol can be preserved for a long time. Second, in the war, hospitals, especially field hospitals, have a great demand for alcohol.
Third, alcohol can be temporarily used as a power source. During the Anti-Japanese War, China's energy was blocked by Japan. In order to ensure transportation in the rear, alcohol is used as a substitute for gasoline. During the whole period of War of Resistance against Japanese Aggression, China's alcohol industry was almost in an explosive state.