The United States froze assets and imposed visa bans on seven Russians close to President Vladimir Putin yesterday and also sanctioned 17 Russian companies in reprisal for Moscow’s actions in Ukraine.

Just over 50 years ago, as the confrontation between the US and Russia over Soviet plans to base nuclear missiles in Cuba moved ever closer to the kind of catastrophe that threatens world stability and peace, or whatever the current version of that is, US President John F Kennedy ordered that all senior American military commanders read Barbara Tuchman’s The Guns of August, the Pulitzer Prize-winning and seminal history of the first months of the First World War.

The mayor of Ukraine’s second-largest city has been shot in the back and pro-Russian insurgents have seized more government buildings in the country as unrest continued.