The US’ Northern Command has sent teams of essential staff deep underground to wait out the Covid-19 pandemic. On the surface, more than a million grunts won’t be quite as cocooned.

Air Force General Terrence O’Shaughnessy heads up the US’ Northern Command, as well as the North American Aerospace Defense Command – a joint US/Canadian operation that monitors the skies over North America for missile and airborne threats. Earlier this week, O’Shaughnessy told reporters via Facebook that some of his watch teams would be moved from their usual command center at Peterson Air Force Base in Colorado to a number of hardened underground bunkers.

One of these facilities is the Cheyenne Mountain bunker complex, a warren of tunnels buried under 2,000 feet (610m) of granite, and sealed behind blast doors designed to withstand a 30 megaton nuclear explosion.