"According to the agreement signed between the Russia and Ukraine in 1999, Russia’s Black Sea Fleet leases a network of over 1,000 naval facilities on the Crimean Peninsula, including a naval base in Sevastopol, two airfields and a training facility in Feodosia. The bases can include up to 25,000 personnel, 22 airplanes, up to 24 artillery complexes, and 132 armored trucks.
“When the agreement was signed no one could have imagined that it would come to this. But as it is, each side can interpret the agreement in its own way, and it will be right,” said Alexei Malashenko, a security expert at Moscow’s Carnegie Center. “Russia says it’s defending its fleet, the other side says it’s violating its sovereignty.”
http://themoscownews.com/news/20140303/192276993/Crimea-crisis-Role-of-Russias-Black-Sea-Fleet.html