The interaction between Russia and Germany in many ways defined the history of the twentieth century. Germany played a major role in both the birth and death of the Soviet Union. World War II in which more than 25 million Soviet citizens perished 1 million alone during the Wehrmachts siege of Leningrad left an indelible legacy on Germany-Russia relations. During Boris Yeltsin last year, the Germany-Russia relationship experienced strains when Gerhard Schroeder became Chancellor and vowed to reassess the sauna diplomacy of the Kohl Yeltsin era. Germany has promoted the NATO-Russia Council and favoured intensifying Russia's contacts with NATO, just as it has opposed what it considers premature NATO enlargement to the former Soviet space, partly because of Russia's opposition. Medvedev's first foreign visitor after his inauguration in May 2008 was Chancellor Merkel. Sergei Prikhodko, his national security advisor, emphasized the symbolic significance of Medvedev's choice of Germany, highlighting the priority that Russia attaches to Germany.