ON MAY 21st, after a nail-biting session of late-night brinkmanship, China and Russiasigned an enormous gas deal worth, at a guess, around $400 billion. Their agreement calls for Russia’s government-controlled Gazprom to supply state-owned China NationalPetroleum Corporation with up to 38 billion cubic metres of gas a year between 2018 and 2048. The deal capped a two-day visit to China by the Russian president, Vladimir Putin, that included a regional-security summit and joint military exercises off the Chinese coast.