(CNN)Here is some background information about the on-going civil war in Syria. Since the war began in 2011, more than 100,000 Syrians have been killed, according to the United Nations. The death toll is no longer being updated by the United Nations due to methodology issues.
Bashar al-Assad has ruled Syria as president since July 2000. His father, Hafez al-Assad, ruled Syria from 1970-2000.
March 2011 - Violence flares in Daraa after a group of teens and children are arrested for writing political graffiti. Dozens of people are killed when security forces crack down on demonstrations.
March 24, 2011 - In response to continuing protests, the Syrian government announces several plans to appease citizens. State employees will receive an immediate salary increase. The government also plans to study lifting Syria's long standing emergency law and the licensing of new political parties.
March 30, 2011 - President al-Assad addresses the nation in a 45-minute televised speech. He acknowledges that the government has not met the people's needs but he does not offer any concrete changes. The state of emergency remains in effect.
April 21, 2011 - Al-Assad lifts the country's 48-year-old state of emergency. He also abolishes the Higher State Security Court and issues a decree "regulating the right to peaceful protest, as one of the basic human rights guaranteed by the Syrian Constitution."
May 18, 2011 - The U.S. imposes sanctions against Syrian President Bashar al-Assad and six other senior Syrian officials. The Treasury Department details the sanctions by saying, "As a result of this action, any property in the United States or in the possession or control of U.S. persons in which the individuals listed in the Annex have an interest is blocked, and U.S. persons are generally prohibited from engaging in transactions with them."
August 18, 2011 - The U.S. imposes new economic sanctions on Syria, freezing Syrian government assets in the U.S., barring Americans from making new investments in the country and prohibiting any U.S. transactions relating to Syrian petroleum products, among other things.
September 2, 2011 - The European Union bans the import of Syrian oil.
September 23, 2011 - The European Union imposes additional sanctions against Syria, due to "the continuing brutal campaign" by the government against its own people.
October 2, 2011 - A new alignment of Syrian opposition groups establishes the Syrian National Council, a framework through which to end President al-Assad's government and establish a democratic system.
October 4, 2011 - Russia and China veto a U.N. Security Council resolution that would call for an immediate halt to the crackdown in Syria against opponents of President Bashar al-Assad. Nine of the 15-member council countries, including the United States, voted in favor of adopting the resolution.
November 12, 2011 - The Arab League suspends Syria's membership, effective November 16, 2011.
November 27, 2011 - Foreign ministers from 19 Arab League countries vote to impose economic sanctions against the Syrian regime for its part in a bloody crackdown on civilian demonstrators.
November 30, 2011 - Turkey announces a series of measures, including financial sanctions, against Syria.
December 19, 2011 - Syria signs an Arab League proposal aimed at ending violence between government forces and protesters.
January 28, 2012 - The Arab League suspends its mission in Syria as violence there continues.
February 2, 2012 - A U.N. Security Council meeting ends with no agreement on a draft resolution intended to pressure Syria to end its months-long crackdown on anti-government demonstrators.
February 4, 2012 - A U.N. Security Council resolution condemning action against Syria is not adopted after Russia and China vote against it.
February 6, 2012 - The U.S. closes its embassy in Damascus and recalls its diplomats.
February 7, 2012 - The Gulf Cooperation Council announces its member states are pulling their ambassadors from Damascus and expelling the Syrian ambassadors in their countries.
February 16, 2012 - The United Nations General Assembly passes a nonbinding resolution endorsing the Arab League plan for Syrian president Bashar al-Assad to step down. The vote was 137 in favor and 12 against, with 17 abstentions.
February 26, 2012 - Syrians vote on the constitutional referendum in polling centers across the country. Almost 90% of voters approve the changes to the constitution.
March 13, 2012 - Kofi Annan, the U.N. special envoy to Syria, meets in Turkey with government officials and Syrian opposition members. He visits Syria over the weekend where he calls for a cease-fire, the release of detainees and allowing unfettered access to relief agencies to deliver much needed aid.
March 15, 2012 - The Gulf Cooperation Council announces that the six member countries will close their Syrian embassies and calls on the international community "to stop what is going on in Syria." The council members include the United Arab Emirates, Bahrain, Saudi Arabia, Oman, Qatar and Kuwait.
March 21, 2012 - After a year of fighting, the U.N. believes more than 8,000 people have died. Opposition activists claim the number to be higher than 10,000 and most of the dead are civilians.
March 27, 2012 - The Syrian government accepts U.N. envoy Kofi Annan's plan to end violence. The proposal seeks to stop the violence, give access to humanitarian agencies, release detainees, and start a political dialogue to address the concerns of the Syrian people.
April 1, 2012 - At a conference in Istanbul, Turkey, the international group Friends of the Syrian People formally recognizes the Syrian National Council as a legitimate representative of the Syrian people.
June 10, 2012 - Abdul Basit Sieda, a Syrian native now living in Sweden, is now Syria's National Council leader.
June 13, 2012 - The U.N. Security Council has authorized up to 300 unarmed military observers for a 90-day mission in Syria. The monitors are tasked with observing a cease-fire that was supposed to go into effect April 12, though both the Syrian regime and opposition have reported at least hundreds of killings since then. In addition, observers are tasked with supporting the implementation of Annan's peace plan, which also calls for access for humanitarian groups, the release of arbitrarily arrested detainees and the start of a political dialogue.
June 16, 2012 - The U.N. suspends its monitoring mission due to intensifying violence.
July 23, 2012 - The Syrian Foreign Ministry spokesman, Jihad Makdissi, threatens to use chemical and biological weapons against outside forces, "No chemical or biological weapons will ever be used, ... unless Syria is exposed to external aggression."
July 30, 2012 - The Syrian Charge d'Affaires in London, Khaled al-Ayoubi, resigns stating he is "no longer willing to represent a regime that has committed such violent and oppressive acts against its own people."
August 2, 2012 - U.N. Secretary General Ban Ki-moon announces that Special Envoy for Syria Kofi Annan will not renew his mandate when it expires at the end of August.
August 6, 2012 - Syrian Prime Minister Riyad al-Hijab's resignation from office and defection from Assad's regime is read on Al Jazeera by his spokesman Muhammad el-Etri. Hijab and his family are said to have left Syria overnight arriving in Jordan. Hijab is the highest-profile official to defect.
August 9, 2012 - Syrian television reports that President al-Assad has appointed Health Minister Wael al-Halki as the new prime minister.
October 3, 2012 - Five people are killed by Syrian shelling in the Turkish border town of Akcakale. In response, Turkey fires on Syrian targets and its parliament authorizes a resolution giving the government permission to deploy its soldiers to foreign countries.
November 11, 2012 - Israel fires warning shots toward Syria after a mortar shell hits an Israeli military post. It is the first time Israel has fired on Syria across the Golan Heights since the 1973 Yom Kippur War.
November 11, 2012 - Syrian opposition factions formally agree to unite as the National Coalition for Syrian Revolutionary and Opposition Forces.
November 13, 2012 - Sheikh Ahmed Moaz al-Khatib is elected leader of the Syrian opposition collective, the National Coalition for Syrian Revolutionary and Opposition Forces.
January 6, 2013 - Assad announces he will not step down and that his vision of Syria's future includes a new constitution and an end to support for the opposition, which he calls terrorists. The opposition refuses to work with Assad's government.
February 12, 2013 - The U.N. Security Council estimates that the number of civilians killed in the two-year civil war in Syria is approaching 70,000.
March 19, 2013 - The National Coalition for Syrian Revolutionary and Opposition Forces elects American-educated Ghassan Hitto as its prime minister. Though born in Damascus, Hitto has spent much of his life in the United States, and holds dual U.S. and Syrian citizenship.
May 6 - A U.S. official tells CNN that Israeli forces conducted an airstrike in Syria on May 5, as well as one the previous week. Sunday's strike targeted a research facility in a mountainous area near Damascus and weapons that were to be transferred to Hezbollah, and the earlier strike targeted Fateh 110 missiles stored at the Damascus airport.
May 17, 2013 - The U.N.'s refugee agency reports that over 1.5 million Syrians have left their country to escape the war.
May 27, 2013 - European Union nations end the arms embargo against the Syrian rebels.
May 27, 2013 - U.S. Senator John McCain visits rebels in Syria. It is reported that he is the highest ranking U.S. official to visit since the beginning of the war.
June 13, 2013 - The Obama Administration says that Syria has crossed a 'red line' with its use of chemical weapons, including the nerve agent sarin gas, against rebels and indicates that it will be stepping up its support of the rebels, who have been calling for the United States and others to provide arms need to battle al-Assad's forces.
July 6, 2013 - Ahmad Assi Jarba is elected the new leader of the Syrian National Coalition.
August 1, 2013 - U.N. spokesman Martin Nesirky tells reporters that a team of ten experts has been assembled to travel to Syria to investigate three reports of chemical weapons use.
August 2, 2013 - The U.N. calls for an investigation into an incident in July in Khan al-Assal in northern Syria. Videos on the internet purport to show Syrian rebels executing as many as 30 people, most of them government soldiers.
August 18, 2013 - A team of U.N. weapons inspectors arrives in Syria to begin an investigation into whether chemical weapons have been used during the civil war.
August 22, 2013 - The United Nations and the United States call for an immediate investigation of Syrian activists' claims that the Bashar al-Assad government used chemical weapons in an attack on civilians on August 21. Anti-regime activist groups in Syria say more than 1,300 people were killed in the attack outside Damascus, many of them women and children. Video footage and witness reports appeared to bolster claims that chemical weapons were used.
August 23, 2013 - U.N. Secretary-General Ban Ki-moon says the use of chemical weapons in Syria is a crime against humanity and must be punished.
August 24, 2013 - Medical charity Doctors Without Borders announces that three hospitals near Damascus treated more than 3,000 patients suffering "neurotoxic symptoms" on August 21. Reportedly, 355 of the patients died.
August 26, 2013 - U.N. inspectors reach the site of a reported chemical attack in Moadamiyet al-Sham, near Damascus. En route to the site, the team's convoy is hit by sniper fire. No one is injured.
August 26, 2013 - U.S. Secretary of State John Kerry describes the suspected chemical weapons attack "inexcusable" and says, "President Obama believes there must be accountability for those who would use the world's most heinous weapons against the world's most vulnerable people."
August 29, 2013 - The U.K.'s Parliament votes against any military action in Syria.
August 30, 2013 - U.S Secretary of State John Kerry says that U.S. intelligence information has found that 1,429 people were killed in last week's chemical weapons attack in Syria, including at least 426 children.
September 10, 2013 - In a speech before the U.S. public, President Obama says he will not, "put American boots on the ground in Syria" but does not rule out other military options.
September 14, 2013 - The U.S. and Russia agree to a plan to eliminate chemical weapons in Syria.
September 16, 2013 - U.N. Secretary-General Ban Ki-moon releases the report from chemical weapons inspectors who investigated the August 21 event. The inspectors say there is "clear and convincing evidence" that sarin was used.
September 20, 2013 - Syria releases an initial report on its chemical weapons program.
September 27, 2013 - The U.N. Security Council passes a resolution requiring Syria to eliminate its arsenal of chemical weapons. President al-Assad says he will abide by the resolution.
September 30, 2013 - At the U.N. General Assembly in New York, Syrian Foreign Minister Walid al-Moualem says that Syria is not engaged in a civil war, but a war on terror.
October 31, 2013 - The Organization for the Prohibition of Chemical Weapons announces that Syria has destroyed all its declared chemical weapons mixing, filling and production facilities.
November 25, 2013 - The U.N. announces that starting January 22 in Geneva, Switzerland, the Syrian government and an unknown number of opposition groups will meet at a "Geneva II" conference meant to broker an end to the Syrian civil war.
December 2, 2013 - U.N. human right chief Navi Pillay says that a U.N. fact-finding team has found "massive evidence" that the highest levels of the Syrian government are responsible for war crimes.
January 20, 2014 - The Syria National Coalition announces it won't participate in the Geneva II talks unless the United Nations rescinds its surprise invitation to Iran or Iran agrees to certain conditions. The U.N. later rescinds Iran's invitation.
January 22, 2014 - In his opening statement at the Geneva II talks, U.S. Secretary of State John Kerry says there is "no way" that Syrian President Bashar al-Assad will be part of a transitional government in the war-ravaged country.
February 13, 2014 - The Organization for the Prohibition of Chemical Weapons tells CNN that Syria has shipped out 11% of its chemical weapons stockpile, falling far short of the February 5 deadline to have all such arms removed from the country.
February 23, 2014 - The U.N. Security Council unanimously passes a resolution boosting access to humanitarian aid in Syria. The resolution also calls for an end to the violence and condemns al Qaeda-affiliated terror attacks.