Deaths of ethnic Azerbaijanis rounded up by police for decades-old murders in a Russian city. The crash of an Azerbaijan Airlines passenger jet that Baku blamed on Moscow. Growing ties between Azerbaijan and Turkey, along with waning Russian influence in the troubled South Caucasus region. These are among the factors that have led to the escalating tensions between Russia and Azerbaijan, the oil-rich Caspian Sea country where President Ilhan Aliyev has been in power since 2003 -- almost as long