Prior to Corona, the military is the only place I had heard the term "essential personnel." In general, active duty military has historically been considered ESSENTIAL. I encountered this the most while stationed at USAFA. On bad weather days, you would see a tiered closure - non-essential would stay home, and essential would report regardless of conditions but dependent on the real needs of your work center. So, in regards to your question - some civilian staff are considered non-essential and the decision is more localized to the specific team. We used to wonder about the kitchen staff workers. It has been said that in certain very bad weather situations, cadets were allowed to work in the kitchen to cook. I can say that I have seen it, but I see how it can happen. The faculty is a mix of civilian and active duty - so there is coverage. Cadet units have active duty leadership, so cadets are not left alone on an island ala Lord of the Flies.