300 nuclear missiles are headed your way. You must respond. What now?

Three hundred nuclear missiles are screaming towards the US. This is likely a pre-emptive strike by Russia to destroy all land-based intercontinental ballistic missile silos in the country. Anti-missile defences cannot knock out many of the incoming rockets, meaning 2 million Americans will die.

Having been sworn in as US president a few minutes previously, I am sitting in the Oval Office watching TV reports of escalating fighting in Europe. A secret service agent bursts into the room and tells me to leave immediately. I take the lift down to the White House crisis centre known as the Situation Room, where I am joined by my top national security officials, who brief me on the incoming attack. I have 15 minutes to respond. As the clock ticks down, I am presented with three options, all of which involve retaliatory strikes against Russia, projected to kill between 5 million and 45 million people. What do I do?

Mercifully, I am watching all this play out through a clunky virtual reality headset strapped to my face. The polygonal avatars in front of me are crude enough that I am never going to mistake this exercise for reality. Even so, my head is spinning and my heart is racing as the drama unfolds amid throbbing alarms and raised voices. For a few minutes, I have been forced to think about the toughest decision that any individual will ever have to make in the history of humanity. The sense of responsibility is crushing. And the words of my national security adviser echo in my ears: “If you do not retaliate and the attack is real, what will you tell the American people afterwards?”