Since declaring independence from the Soviet Union over 30 years ago, Ukraine has endured internal political upheaval and conflict with its neighbour.
With the country at war with Russia, here is a timeline of the main events in Ukraine's political history since it won independence from Moscow in 1991.
Independence from Moscow
1991: Leonid Kravchuk, leader of the Soviet republic of Ukraine, declares independence from Moscow. In a referendum and presidential election, Ukrainians approve independence and elect Kravchuk president.
1994: Leonid Kuchma beats Kravchuk in a presidential election deemed largely free and fair by observers.
1999: Kuchma is re-elected in a vote riddled with irregularities.
Orange Revolution begins
2004: Pro-Russian candidate Viktor Yanukovich is declared president but allegations of vote rigging trigger protests in what becomes known as the Orange Revolution, forcing a re-run of the vote. Pro-Western former prime minister Viktor Yushchenko is elected president.
2005: Yushchenko takes power with promises to lead Ukraine out of the Kremlin's orbit, towards NATO and the EU. He appoints former energy company boss Yulia Tymoshenko as prime minister but after in-fighting in the pro-Western camp, she is sacked.
2008: NATO promises Ukraine it will one day join the alliance. Russian President Vladimir Putin says Moscow would see any eastward expansion of the alliance as a direct threat to Russia.
Violent anti-government protests
2010: Yanukovich defeats Tymoshenko in a presidential election. Russia and Ukraine clinch a gas-pricing deal in exchange for extending the lease for the Russian navy in a Ukrainian Black Sea port. Fighting breaks out in parliament over the deal.
2013: Yanukovich's government suspends trade and association talks with the EU in November and opts to revive economic ties with Moscow, triggering months of mass rallies in Kyiv.
2014: The protests, largely focused around Kyiv's Maidan square, turn violent. Dozens of protesters are killed.
Crimea annexed by Russia, conflict begins in east Ukraine
February 2014: The parliament votes to remove Yanukovich, who flees. Within days, armed men seize parliament in the Ukrainian region of Crimea and raise the Russian flag. Moscow annexes the territory after a March 16 referendum which shows overwhelming support in Crimea for joining the Russian Federation.
April 2014: Pro-Russian separatists in the eastern region of Donbas declare independence. Fighting breaks out, which has continued sporadically into 2022, despite frequent ceasefires.
May 2014: Ukrainian billionaire Petro Poroshenko wins a presidential election with a pro-Western agenda.
July 2014: A missile brings down passenger plane MH17 over eastern Ukraine, killing all 298 people on board. Investigators trace back the weapon used to Russia, which denies involvement.
2017: An association agreement between Ukraine and the EU opens markets for free trade of goods and services, and visa-free travel to the EU for Ukrainians.
2019: A new Ukrainian Orthodox church wins formal recognition, angering the Kremlin.
Zelenskyy elected
April 2019: Former comic actor Volodymyr Zelenskyy defeats Poroshenko in a presidential election on promises to tackle corruption and end the war in eastern Ukraine. His Servant of the People party wins a July parliamentary election.
June 2020: The IMF approves a $US5 billion lifeline to help Ukraine stave off default during a pandemic-induced recession.
January 2021: Zelenskyy appeals to Biden, now US president, to let Ukraine join NATO.
February 2021: Zelenskyy's government imposes sanctions on Viktor Medvedchuk, an opposition leader and the Kremlin's most prominent ally in Ukraine.
Russian troops build up on border
Spring 2021: Russia masses troops near Ukraine's borders in what it says are training exercises.
October 2021: Ukraine uses a Turkish Bayraktar TB2 drone for the first time in eastern Ukraine, angering Russia.
Autumn 2021: Russia again begins massing troops near Ukraine.
December 7, 2021: Biden warns Russia of sweeping Western economic sanctions if it invades Ukraine.
December 17: Russia presents detailed security demands including a legally binding guarantee that NATO will give up any military activity in eastern Europe and Ukraine.
January 2022: Russian forces arrive in Belarus, to the north of Ukraine, for joint drills. Washington presents a written response to Russia's security demands, repeating a commitment to NATO's "open-door" policy while offering "pragmatic" discussions of Moscow's concerns. President Vladimir Putin says Russia's main security demands have not been addressed.
February 2: The United States says it will send 3,000 extra troops to Poland and Romania to help shield NATO allies in eastern Europe from any spillover from the crisis.
February 4: Putin, at the Beijing Winter Olympics, wins Chinese support for his demand that Ukraine not be allowed to join NATO.
February 7: French President Emmanuel Macron sees some hope for a diplomatic resolution of the crisis after meeting Putin in the Kremlin. Macron then visits Kyiv and praises the "sang-froid", or composure, of Zelenskyy and the Ukrainian people.
February 15: Russia says some of its troops are returning to base after exercises near Ukraine and mocks Western warnings about a looming invasion. Russia's parliament asks Putin to recognise as independent two Russian-backed breakaway regions in eastern Ukraine.
February 18: US ambassador to the Organisation for Security and Cooperation in Europe Michael Carpenter says Russia has probably massed between 169,000-190,000 personnel in and near Ukraine.
February 19: Russia's strategic nuclear forces hold exercises overseen by Putin.
Russia recognises breakaway regions
February 21: Macron says Biden and Putin have agreed in principle to a summit over Ukraine.
In a televised address, Putin says Ukraine is an integral part of Russian history, has never had a history of genuine statehood, is managed by foreign powers and has a puppet regime. Putin signs agreements to recognise breakaway regions in eastern Ukraine as independent and order Russian troops there.
February 22: US, UK and their allies enact sanctions on Russian parliament members, banks and other assets. Germany halts final certification of the Nord Stream 2 pipeline that was still waiting for approval.
Putin, in a television address, demands Ukraine demilitarise and says the Minsk peace agreement over breakaway republics no longer exists, blaming Kyiv for killing the deal.
Russia begins attack on Ukraine
February 24: Russian President Putin authorises "special military operations" in eastern Ukraine and asks Ukrainian forces to lay down their arms in a televised address. Russian forces begin missile and artillery attacks on Ukrainian forces and air bases, striking areas in major cities.
Since the start of the conflict, Ukrainian cities have been targeted by heavy shelling from Russian forces, and both sides have reported significant casualties.
The worsening crisis has prompted millions of Ukrainians to flee to neighbouring countries — the majority being women and children, as most Ukrainian men aged between 18 and 60 have been barred from leaving.
Millions more who remain in Ukraine are internally displaced by the conflict that shows no signs of immediate resolution, with talks between Ukrainian and Russian diplomats failing to reach any resolution.
ABC/wires
