The Crimean peninsula, the main flashpoint in Ukraine's crisis, is a pro-Russia part of Ukraine separated from the rest of the country geographically, historically and politically. It also hosts Russia's Black Sea Fleet. Ukraine has accused Russia of invading it. Here's some key information about the region:
ON THE BLACK SEA
The Crimean Peninsula juts into the Black Sea, all but an island except for a narrow strip of land in the north connecting it to the mainland. On its eastern shore, a finger of land reaches out almost to Russia. It's best known in the West as the site of the 1945 Yalta Conference, where Soviet dictator Josef Stalin, President Franklin D. Roosevelt and British Prime Minister Winston Churchill sealed the postwar division of Europe.
WHY IT'S PART OF UKRAINE
It only became part of Ukraine when Soviet leader Nikita Khrushchev gave the peninsula to his native land in 1954. This hardly mattered until the Soviet Union broke up in 1991 and Crimea ended up in an independent Ukraine. Despite that, nearly 60 percent of its population of 2 million identify themselves as Russians.
THE BLACK SEA FLEET
On Crimea's southern shore sits the port city of Sevastopol, home to the Russian Black Sea Fleet and its thousands of naval personnel. Russia kept its half of the Soviet fleet, but was rattled in 2009 when the pro-Western Ukrainian President Viktor Yuschenko warned that it would have to leave the key port by 2017. Shortly after pro-Russian Viktor Yanukovych was elected president in 2010, he agreed to extend the Russian lease until 2042. Russia fears that Ukraine's new pro-Western government could evict it.
The 1991 fall of the Soviet Union also brought the return of the Crimean Tatars, the native hosts of the land that fell to Russia under Catherine the Great in the 18th century. They were brutally deported in 1944 under Stalin. The Crimean Tatars, who now make up about 12 percent of its population, have sided with the anti-Yanukovych protesters in Kiev who drove his government from power.
British nurse Florence Nightingale was celebrated for treating wounded soldiers during the Crimean War of the mid-19th century, which Russia lost to an alliance that included Britain, France and the Ottoman Empire. She is now considered the founder of modern nursing.