‘What follows plague?’ I asked a medieval historian at the start of the pandemic. ‘War,’ he replied. In recent days, this remark has seemed worryingly prescient: 120,000 Russian troops are massing on the border with Ukraine, China is aggressively increasing military activity across the Taiwan Strait and Iran has responded to Israel’s successful sabotage of its nuclear facility by declaring it will enrich uranium to close to the level required for a nuclear bomb.