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:
Located on the Black Sea
The Crimean Peninsula extends 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. Russia plans to build a bridge across the strait.
With an area of 27,000 square kilometers (10,000 square miles), it is slightly smaller than Belgium. It is Ukraine's only formally autonomous region, with Simferopol as its capital. Sevastopol has a separate status within Ukraine.
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.
Crimea was absorbed into the Russian empire along with most of ethnic Ukrainian territory by Catherine the Great in the 18th century. Russia's Black Sea naval base at Sevastopol was founded soon afterwards.
More than half a million people were killed in the Crimean War of 1853-56 between Russia and the Ottoman Empire, which was backed by Britain and France. The conflict reshaped Europe and paved the way for World War One.
In 1921, the peninsula, then populated mainly by Muslim Tatars, became part of the Soviet Union. The Tatars were deported en masse by Soviet leader Joseph Stalin at the end of World War Two for alleged collaboration with the Nazis.
Why Crimea is part of Ukraine
Crimea 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.
Since the collapse of the Soviet Union in 1991, there have been periodic political tussles between over its status between Moscow and Kiev.
Around 2 million. Ukraine's 2001 census showed around 58 percent were ethnic Russian, 24 percent ethnic Ukrainian and 12 percent Tatars, who support the new pro-Western government in Kiev.
Crimea's temperate climate makes it a popular tourist destination for Ukrainians and Russians, especially Yalta, where the Soviet, U.S. and British victors of World War Two met in 1945 to discuss the future shape of Europe.
It accounts for three percent of Ukraine's gross domestic product, with 60 percent of its own output made up by services. The land is intensely farmed, with wheat, corn and sunflowers the main crops. Extra water supplies are brought by canal from Ukraine's Dnieper River.
There are chemical processing plants and iron ore is mined in Kerch. Ukraine has two grain terminals in Crimea - in Kerch and in Sevastopol. According to UkrAgroConsult, these have exported 1.6 million tons of grain so far this season or 6.6 percent of Ukraine's total exports.
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 in exchange for discounts on Russian gas supplies. Russia fears that Ukraine's new pro-Western government could evict it.
Russia's Black Sea base in Sevastopol gives Moscow access to the Mediterranean. Ukraine's fleet, carved out of the same Soviet fleet as Russia's, is also based there.
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.
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