We can get some clues about which items will disappear first during a major national emergency by taking a look at where such a scenario is already playing out. One recent survey found that over 80 percent of all basic foodstuffs are currently unavailable in Venezuela, and about half the country can no longer provide three meals a day for their families. Thankfully, some stores still have a few things that they are able to offer, but other key items are completely gone.When I was running and maintaining a bunch of rental houses, I was amazed how many tenants had near empty pantries and seemed to depend on fast food or daily trips to the store for their meals.
Government disaster planners encourage people to have enough necessities like food and water on hand for emergencies,, and that's well below the two-week threshold established by Civil Defense planners in the Cold War era.
Two weeks seems like an easy threshold to meet. Two months could be accomplished with a little thought and planning, and done in a way that builds on items you'll eventually use anyway.