The Russian Fleet has been operating in the Black Sea and the Mediterranean Sea since the late 18th century. Since then the principal base of the Russian Black Sea Fleet was located Sevastopol on the Crimean peninsula, which fell under jurisdiction of the Ukraine after the breakup of the Soviet Union. This led to conflicts between the two former Soviet countries.
To ease the tensions, the two governments signed several treaties and in 1997 partitioned the fleet, dividing armaments and bases between them. Ukraine agreed to lease its bases to the Russian Black Sea Fleet until 2017. However, the announcement that the lease of Russian naval bases would not be extended beyond 2017 led to renewed tension which were eased in 2010, when the two countries reached an agreement whereby the Russian lease of naval facilities would be extended by 25 years in exchange for providing Ukraine with discounted Russian natural gas. This deal remains controversial in Ukraine. While the pro-Russian government of president Yanukovych rules in the Ukraine the tension have lessened considerably – but are certainly to flare up if the tide shifts in Ukraine.