3 Ukraine gained independence after the collapse of the Soviet Union in 1991. Since then it has veered between seeking closer integration with Western Europe and reconciliation with Russia.
4 The recent protests began in November after President Viktor Yanukovych, who was ousted last month, refused to sign a wide-ranging free trade and association agreement with the European Union which many hoped would lead to economic benefits. Yanukovych had resisted EU demands to free Yulia Tymoshenko, his pro-EU opponent jailed in 2011. Russian President Vladimir Putin wasn't happy and Moscow, which buys more than half of Ukraine's exports, threatened to shut borders and pipelines if Yanukovych signed with the EU.
5 Ukraine's economy has struggled since communism crashed - GDP per head is barely a quarter that of resource-rich Russia and half that of the poorest EU state. Its dependence on steel exports makes it vulnerable to global financial turmoil. Ukraine received a multibillion-dollar loan from the IMF in 2008 but a further loan approved in 2010 was frozen.
6 Although it doesn't hold the economic power it once did, Ukraine is strategically important because of its geography. Russia supplies about 25 per cent of Europe's gas needs, half of which is pumped along pipelines running through Ukraine. Moscow has cut off that flow in past disputes with Kiev and a disruption could push up energy prices for both businesses and households.
7 The unrest in Ukraine has shifted to the Crimean peninsula which juts into the Black Sea, with Russian troops seizing airports and strategic locations. Since 1783 Russia has based its Black Sea fleet on the area's southern shore at the port city of Sevastopol. It also has thousands of naval personnel stationed there. In 2009, the pro-Western Ukrainian President Viktor Yuschenko warned that the fleet would have to leave the port by 2017. In 2010, the pro-Russian President Viktor Yanukovych agreed to extend the Russian lease to 2042.
8 Crimea became part of Ukraine only when Soviet leader Nikita Khrushchev gave the peninsula to his native land in 1954. Nearly 60 per cent of its 2 million population identify as Russian. Since Yanukovych was ousted on February 21, there are calls for the Crimea to secede from the rest of the country.
9 Russian intervention in Crimea has raised the stakes in Ukraine. Its interim leaders have called it an "armed invasion" while US President Barack Obama urged Putin to "de-escalate tensions by withdrawing its forces". Putin said Russia maintained its right to protect its interests and the Russian-speaking population of Crimea.
10 Western leaders are looking to put pressure on Moscow through sanctions. Ukraine's military are on combat alert. However, in the event of an armed conflict, Ukraine's military is no match for Russia's. It has around 130,000 troops compared with around 850,000 in Russia, while in Crimea it has about 3500 troops compared with the more than 20,000 Russian personnel in the area.
