MOSCOW – In recent days, Russian President Dmitry Medvedev has moved against some of the most powerful men in the Kremlin, including Igor Sechin, a deputy prime minister who is perhaps the closest figure to Prime Minister Vladimir Putin – and who is also the chairman of Rosneft, Russia’s largest oil firm. A decree signed by Medvedev with the stated purpose of improving the country’s investment climate will strip Sechin and others of their chairmanships of some of Russia’s biggest state-owned companies.