Despite being a recognized independent country since 1991, as a former USSR constituent republic, Ukraine had been perceived by the leadership of Russia as being part of its sphere of influence. In 2008, Russian President Vladimir Putin spoke out against Ukraine's membership in NATO.[2][3] In 2009, Romanian analyst Iulian Chifu and his co-authors opined that in regard to Ukraine, Russia has pursued an updated version of the Brezhnev Doctrine, which dictates that the sovereignty of Ukraine cannot be larger than that of the Warsaw Pact's member states prior to the collapse of the Soviet sphere of influence during the late-1980s and early-1990s.[4] This view is built upon the premise that Russia's actions to placate the West in the early 1990s should have been met with reciprocity from the West, without NATO expansion along Russia's border.[5]