03/25/2014 06:32 EDT | Updated 05/25/2014 05:59 EDT

Timeline: Ukraine political developments since independence in 1991

Ukraine declared its independence from the Soviet Union on Aug. 24, 1991, by stating it would no longer follow Soviet law and it formalized the break Dec. 1 through a countrywide referendum in which independence had the support of 90 per cent of voters and 56 per cent of those in Crimea. Here is a chronology of some notable political developments involving Ukraine since then:

Dec. 2, 1991: Canada is among the first countries to recognize Ukraine as an independent power.

Dec. 5, 1991: Ukraine holds its first presidential elections, voting Leonid Kravchuk into the top job.

July. 10, 1994: Leonid Kuchma, former Ukrainian prime minister who favoured closer ties with Russia over the West, becomes president in the country's second election.

Dec. 5, 1994: Ukraine becomes a signatory to the Budapest Memorandum of Security Assurances, an international treaty guaranteeing major nuclear powers would respect Ukraine's independence if the country surrendered its inherited stockpile of nuclear weapons. The U.S. and Russia are among the nuclear powers that sign the deal.

June 1, 1996: Ukraine finishes complying with the terms of the Budapest memorandum by sending the last of its nuclear warheads to Russia for destruction.

June 28, 1996: Ukraine adopts and formalizes its own constitution.

Nov. 14, 1999: Kuchma is re-elected Ukrainian president

Nov. 28, 2000: One of Kuchma's political rivals publicly accuses him of involvement in the abduction and murder of Ukrainian journalist Georgiy Gongades, citing tapes from one of Kuchma's bodyguards as evidence. A stream of other tapes was eventually released, leading to months of protests in Kyiv and a drop in Kuchma's popularity.

2001: Protests continue to ramp up, eventually labelled as the "Ukraine Without Kuchma" movement. The protests are eventually quashed by the government, but political opposition gains strength as a result of the anti-Kuchma sentiment.

March 31, 2002: A hotly contested election, rife with allegations of corruption and media censorship, takes place. The party endorsed by Kuchma narrowly maintains its status as the largest bloc in parliament, while an opposition party headed by Viktor Yushchenko emerges as a powerful political force. Kuchma promises to step down as president in 2004.

May 2003: Yushchenko makes a week-long visit to Canada to tout his vision for a more democratic Ukraine.

September 2004: During a presidential election campaign, Yushchenko falls gravely ill from what was later found to be dioxin poisoning. He recovers.

Nov. 21, 2004: Yushchenko squares off against pro-Russia candidate Victor Yanukovych in an election, losing narrowly. However international observers make allegations of election fraud and Yushchenko challenges the results. Largely peaceful protests eventually dubbed the Orange Revolution keep up political pressure.

Dec. 3, 2004: The Ukrainian Supreme Court annuls the result and ordered a new vote.

Dec. 26, 2004: Another vote is held in which Yushchenko is declared the winner and becomes president.

Jan. 24, 2005: Yushchenko names Yulia Tymoshenko, then a political ally and Orange Revolution leader, as prime minister.

Sept. 8, 2005: Yushchenko dismisses the government and fires Tymoshenko amid escalating tensions within parliament and claims of corruption. This is the start of a complex political chess match during which political alliances change frequently.

Aug. 4, 2006: Yushchenko appoints former rival Yanukovych as prime minister.

April 2, 2007: Yushchenko signs an order to dissolve parliament and call an election, an action that is deemed unconstitutional, and parliament appeals the move to the country's constitutional court.

May 2007: Yushchenko dismisses three members of the constitutional court, effectively preventing them from ruling on the appeal and clearing the way for elections to proceed.

Sept. 30, 2007: Parliamentary elections, which don't affect the post of president, are held. The result sees Yushchenko's and Tymoshenko's political camps join forces once again.

Dec. 18, 2007: Tymoshenko is reappointed prime minister.

August 2008: Yushchenko and Tymoshenko clash publicly over the war between Russia and Georgia. Yushchenko strongly condemns Russia, while Tymoshenko advocates for the country to take a more neutral position.

September 2008: Yushchenko and his party withdraw from the governing coalition after Tymoshenko votes in favour of a bill to limit presidential powers. The breakdown of the coalition could have triggered yet another election, but a new coalition involving both Yushchenko and Tymoshenko is eventually formed.

January 2009: The government is forced to cope with a gas crisis after Russia temporarily stops piping gas to the country. The halt was due to contentious contract negotiations and claims of unpaid debts. New contracts are struck later that month and gas flow resumes.

Feb. 7, 2010: Presidential elections are held, in which Yanukovych becomes the country's new leader. Tymoshenko comes a close second in the race, while Yushchenko fares poorly. Tymoshenko publicly questions the fairness of the election and publicly states that she does not recognize Yanukovych as president.

March 4, 2010: Tymoshenko resigns as prime minister after her government loses a vote of non-confidence.

Dec. 20: Tymoshenko is charged with misuse of government funds

Jan. 27, 2011: Tymoshenko is hit with more corruption charges, this time accused of using medical vehicles for campaigning purposes. More charges follow in the following months, all of which she condemns as politically motivated. International powers including the United States, the European Union and NATO, roundly criticize the legal proceedings against her.

Oct. 11, 2011: Tymoshenko is found guilty of abuse of power. She is sentenced to seven years in prison and barred from seeking political office during her term.

Oct. 12, 2012: Another parliamentary election is held, again amid allegations of bribery and voter fraud.

Nov. 21, 2013: Yanukovych's government announces it is abandoning an agreement that would strengthen ties with the European Union and instead seeks closer co-operation with Moscow. Protesters take to the streets.

Nov. 30, 2013: Images of protesters bloodied by police truncheons spread quickly and galvanize public support for the demonstrations.

Dec. 1, 2013: A protest attracts around 300,000 people in Kyiv's Independence Square, known as the Maidan, the largest since the Orange Revolution in 2004. Activists seize Kyiv City Hall.

Dec. 17, 2013: Russian President Vladimir Putin announces that Moscow will buy $15 billion worth of Ukrainian government bonds and allow for a sharp cut in the price Ukrainians pay for Russian natural gas.

Jan. 22, 2014: Protests grow deadly as three demonstrators are killed during clashes with police

Jan. 28, 2014: The prime minister resigns and parliament repeals harsh anti-protest laws that set off the violence of a week earlier. Both are concessions to the opposition aimed at defusing the crisis.

Feb. 18, 2014: Street clashes erupt, leaving at least 26 dead and hundreds injured. The violence begins when protesters attack police lines and set fires outside parliament after it stalls on taking up a constitutional reform to limit presidential powers. Russia's offer the day before to resume payments under the bailout deal also feeds opposition suspicions that Yanukovych has made a deal with Moscow to stand firm against the protesters. Riot police respond to the violence by trying to push protesters out of Independence Square.

Feb. 20, 2014: Hours after a truce is announced, violence resumes with snipers shooting protesters from the roofs. Most of the 82 people who died in several days of violence were killed on that day.

Feb. 21, 2014: Under a European-mediated plan, protest leaders and Yanukovych agree to form a new government and hold an early election. Parliament slashes his powers and votes to free Tymoshenko from prison. Yanukovych flees Kyiv after protesters take control of the capital.

Feb. 22, 2014: Parliament votes to remove Yanukovych and hold new elections. Tymoshenko is freed from prison and speaks from a wheelchair to tens of thousands who gather on the Maidan.

Feb. 23, 2014: Ukraine's parliament assigns presidential powers to its new speaker, Oleksandr Turchinov, an ally of Tymoshenko. The new authorities ask the West for loans to avoid an imminent default. Pro-Russia protesters start rallying against the new authorities in Crimea, where Russia has a major naval base.

Feb. 25, 2014: Rallies in Crimea against "the bandits" in Kyiv continue. A Russian lawmaker promises that Moscow will protect them.

Feb. 26, 2014: Leaders of Ukraine's protest movement propose top legislator Arseniy Yatsenyuk as the country's next prime minister. In Moscow, Putin orders major military exercises just across the border in a show of force and apparent displeasure over the country's new direction.

Feb. 27, 2014: Masked gunmen seize regional parliament and government buildings in Crimea. Ukraine's newly formed government pledges to prevent a national breakup with strong backing from the West. Yanukovych is granted refuge in Russia.

Feb. 28, 2014: Ukraine says Russian troops have taken up positions around a coast guard base and two airports on its Crimea peninsula. In Kyiv, Ukraine's parliament adopts a resolution demanding that Russia halt steps it says are aimed against Ukraine's sovereignty and territorial integrity. Yanukovych makes his first public appearance, in southern Russia, since fleeing Ukraine. He says he was "forced" to do so and promises to "keep fighting for the future of Ukraine."

March 1, 2014: Hundreds of Russian troops head to the Crimean Peninsula despite Western pleas for Putin to pull them back.

March 3, 2014: Russian troops seize a ferry terminal in the city of Kerch, which offers direct access to Russia.

March 6, 2014: Officials in Crimea announce they will hold a referendum on Mar. 16 to determine whether residents want independence from Ukraine. Western countries including Canada quickly denounce the plan and say they won't recognize the result. A referendum had been already scheduled in Crimea on March 30, but the question to be put to voters was on whether their region should enjoy ``state autonomy'' within Ukraine.

March 15, 2014: The United Nations security council votes on a resolution declaring the Crimea referendum illegal. Most countries support the motion, but Russia exercises its veto power to kill the resolution. China abstains, which is taken as a sign of solidarity with the West.

March 16, 2014: The referendum is held in Crimea under a heavy Russian military presence. The results overwhelmingly back annexation into Russia.

March 17, 2014: The United States, the European Union and Canada all impose the first of several sanctions in protest of Russia's actions.

March 18, 2014: As Putin begins the process of formally annexing Crimea, two people were killed at a Ukrainian military base when unknown gunmen stormed the base.

March 19, 2014: Ukraine pledges to withdraw troops from Crimea as Russian troops seized control of Ukrainian naval headquarters in the region. Ukraine also announces its intention to withdraw from the Moscow-dominated Commonwealth of Independent States, a loose alliance of 11 former Soviet nations.

March 21, 2014: Putin signs a law formally completing the annexation of the Crimean Peninsula. At the same time, Yatsenyuk signs the political association agreement with the European Union that Yanukovych originally rejected, touching off the crisis in the first place.

March 22, 2014: Thousands of protesters gather in the eastern Ukrainian city of Donetsk to call for a referendum that would allow the region to become part of Russia.

March 23, 2014: Russian troops storm a Ukrainian air force base in Crimea, capturing an air force commander and injuring at least one other person. This is the first in a series of attacks on Ukrainian military bases in the region.

March 24, 2014: Seven out of eight members of the Group of Eight, including Canada, announce they are suspending co-operation with Russia and effectively shutting the country out of the collective. The move is meant to punish Russia for its annexation of Crimea. Russia shrugs off the decision. At the United Nation, Ukraine submits a resolution calling on all 193 member countries not to recognize any changes in Crimea's status.

March 25, 2014: Ukrainian troops officially withdraw from the Crimean peninsula as the defence minister resigns his post.