(Reuters.) Russia is assembling troops in Ukraine. The West threatened sanctions if Russia launched an invasion. Moscow claims it does not plan an invasion, but in tension has asked for broad Western security assurances.

Below is a chronological listing of major events in Ukraine’s political history from 1991 when it was independent from Moscow.

* 1991: Leonid Kravchuk, leader of the Soviet republic of Ukraine, declares independence from Moscow. Ukrainians vote in a referendum to approve independence.

* 1994: Kravchuk loses a presidential election to Leonid Kuchma, also a former communist, in elections deemed largely free and fair by observers.

* 1999: Kuchma is re-elected in 1999 in a vote riddled with irregularities.

* 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. Viktor Yushchenko is elected as the president. He was a former pro-Western prime minister.

* 2005: Yushchenko takes power with promises to lead Ukraine out of the Kremlin’s orbit, towards NATO and the EU. Yulia Tymoshenko, a former boss of an energy company, is appointed as the prime minister. However, there was infighting within Ukraine’s pro Western camp and she is forced to resign.

* 2008: NATO promises Ukraine it will one day join the alliance.

* 2010: Yanukovich defeats Tymoshenko in a presidential election. Russia and Ukraine reach a deal on gas pricing in return for the extension to the lease of the Russian naval vessel in a Black Sea port.

* 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 are killed by protesters. The parliament elects Yanukovich to be removed in February. Yanukovich flees. Soon after, Russian-armed men take control of the Ukrainian regional government in Crimea. Moscow annexes Crimea after the March 16 referendum, which showed overwhelming support from Crimea to join the Russian Federation.

April: The eastern Donbass pro-Russian separatists proclaim independence. In spite of numerous ceasefires, fighting broke out and has continued to flare up until 2022.

Businessman Petro Poroshenko is elected president with pro-Western policies in May.

A missile crashes passenger jet MH17 on its way from Amsterdam to Kuala Lumpur in July killing 298 of the passengers. Russian investigators deny involvement in the use of this weapon.

* 2017: An association agreement between Ukraine and the EU is passed, opening 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.

Volodymyr Zelenskiy, a former actor and comedian, defeats Poroshenko during an April presidential election. He promises to fight corruption and put an end to the conflict in eastern Ukraine. A July parliamentary election is won by the Servant of the People.

In July 2017, the U.S. president Donald Trump requests Zelenskiy’s assistance to examine Joe Biden and Hunter Biden about possible business transactions in Ukraine. The attempt to impeach Trump fails, as does the call.

* March 2020 – Ukraine goes into its first lockdown to curb COVID-19.

* June 2020 – IMF approves a $5 billion lifeline to help Ukraine stave off default during a pandemic-induced recession.

* Jan. 2021 – Zelenskiy appeals to Biden, who is now U.S. president, for Ukraine to join NATO.

* Feb. 2021 – Zelenskiy’s government imposes sanctions on Viktor Medvedchuk, an opposition leader and the Kremlin’s most prominent ally in Ukraine.

* Spring 2021 – Russia masses troops near Ukraine’s borders. The Russians claim that they were conducting a training exercise.

* Oct. 2021 – Ukraine uses a Turkish Bayraktar TB2 drone for first time in eastern Ukraine, angering Russia.

* Autumn 2021 – Russia again begins massing troops near Ukraine.

* Dec. 7 – Biden warns Russia of sweeping Western economic sanctions if it invades Ukraine.

* Dec 17 – Russia presents detailed security demands including a legally binding guarantee that NATO will give up any military activity in eastern Europe and Ukraine.

* Jan 10 – U.S. and Russian diplomats fail to narrow differences on Ukraine, and subsequent talks also bring no major breakthrough.

* Jan 14 – A cyberattack warning Ukrainians to “be afraid and expect the worst” hits Ukrainian government websites.

* Jan. 17 – Poroshenko returns to Ukraine to face charges in a treason case. Russian troops arrive in Belarus to conduct joint drills.

* Jan 24 – NATO puts forces on standby and reinforces eastern Europe with more ships and fighter jets. Some Western nations begin to evacuate non-essential diplomat staff from Kyiv.

* Jan 26 – Washington presents a written response to Russia’s security demands, repeating a commitment to NATO’s “open-door” policy while offering a “principled and pragmatic evaluation” of Moscow’s concerns.

* Jan 28 – Putin says Russia’s main security demands have not been addressed but that Moscow is ready to keep talking.