Japan and UK recommending 3 days' worth of food and water?

Disclaimer
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News has emerged that the Japanese and British governments have recommended preparing three days' worth of emergency food and water. It appears to be a type of guideline...
It is ambiguous whether this is preparation for natural disasters or an indication of an outbreak of war. The security crisis in the Far East Asia is also an issue.
It is known that Japan prepares emergency food and relief supplies under government leadership to prepare for disasters.
However, if a disaster situation is widespread, it becomes extremely difficult to disperse items such as disaster relief supplies.
Therefore, if citizens prepare emergency food themselves, their chances of survival increase accordingly.
Many countries are choosing strategies to minimize damage in preparation for catastrophes.