Former Russian Defense Minister and Kremlin chief of staff Sergei Ivanov, once considered a possible successor to the Kremlin leader Vladimir Putin, has died at the age of 73.According to Reuters, Ivanov’s death was first announced on Friday by the VTB United League basketball organization, where he served as an honorary president, before being confirmed by the Kremlin. No cause of death was given.JOIN US ON TELEGRAMFollow our coverage of the war on the @Kyivpost_official.“Vladimir Putin expressed his deepest condolences to the family and friends of Sergei Ivanov on his passing,” the Kremlin said in a brief statement.A career built in the KGB’s shadowIvanov was born in Leningrad, now St. Petersburg, where he studied languages before being recruited into the Soviet KGB – the same institution that shaped Putin’s early career. The two worked together at the beginning of their careers, forming a relationship that would later prove decisive. After the collapse of the Soviet Union, Ivanov rose through the KGB’s successor organizations to become a deputy director of the Federal Security Service (FSB) under Putin.In 2001, Ivanov was appointed defense minister, becoming Russia’s first civilian defense minister. In that role, he oversaw Russia’s armed forces during the second Chechen war.Chechnya.He became deputy prime minister in 2005, and first deputy prime minister in 2007, which briefly placed him among the leading candidates to succeed Putin as president.Sidelined after years at the topUltimately, Putin chose Dmitry Medvedev as his successor for the 2008 presidential term, while Ivanov remained in government as deputy prime minister and later Kremlin chief of staff.