OP here - turns out we aren't essential, but my boss "fought" to have us have to return to the office - there are no other civilians are in.
That said, how they are understanding it is that if I have to take leave, it's considered a furlough and they issue another furlough notice. Which, they understand, is still going to be due back pay.
So....that's what I know now. And not sure how right it is.