Here is a timeline of President Ali Abdullah Saleh's 32-year rule in Yemen:
July 1978 - Saleh takes power in the former North Yemen.
February 1979 - Saleh crushes an attempt to overthrow him.
May 1990 - Pro-Western North Yemen and socialist South Yemen merge after 300 years of separation to form a powerful new republic dominating the strategic entrance to the Red Sea.
-- North Yemeni leader Saleh proclaims unification in Aden after the parliaments of both states elect him president.
July 1994 - Northern Yemen declares the almost three-month Yemeni civil war is over after gaining control of Aden, its southern foe's last bastion and ending a bid to revive an independent state.
-- Sanaa declares that former vice-president Ali Salem al-Baidh and his supporters who tried to secede from a four-year merger with the north have been defeated that unity is assured.
-- Southern leaders led by Baidh, who set up a breakaway southern state on May 21, are forced to flee into exile.
October 2000 - Bombing of USS Cole in Aden harbor kills 17 sailors and blows hole in navy vessel's hull.
November 2001 - Saleh declares support for U.S. "war on terror."
February 2008 -- A fragile truce is signed with North Yemen's Houthis, Zaidi Shi'ite tribes, but clashes soon resume in a four-year revolt in the northwest region of Saada. Saleh unilaterally declares the war over in July 2008. However, full-scale fighting resumes a year later.
January 2009 - Al Qaeda's Yemeni and Saudi wings merge in a new group called al Qaeda in the Arabian Peninsula (AQAP) led by Nasser al-Wahayshi.
November 2009 - Saudi Arabia launches a military offensive against rebels after a cross-border incursion.
-- The Houthi deny accusations that infiltrators entered Saudi territory and call the offensive against the group "unjustified," accusing it of mainly targeting civilians.
January 2010 - A meeting of Western and Gulf foreign ministers in London aims to bolster Yemen's fight against al Qaeda.
February 2010 - Yemen and northern Shi'ite rebels agree to a truce aimed at ending the war.
February 2011 - Saleh says he will not seek to extend his presidency beyond his current term, which expires in 2013.
-- A day of anti-government protests on February 3 attracts more than 20,000 people on to the streets in Sanaa.
March 2011 - The opposition presents Saleh on March 2 with a road map for a smooth transition of power, offering him a graceful exit.
-- Saleh, hoping to defuse increasingly violent protests, says he will draw up a new constitution to create a parliamentary system of government. An opposition spokesman swiftly rejects the proposal.
-- Snipers kill 52 protesters among crowds that flocked to a sit-in at Sanaa University after Friday prayers on March 18. The killings prompt Saleh to declare a state of emergency for 30 days that restricts freedom of movement and the right to gather and gives police more powers to make arrests. The tourism minister and head of the ruling party's foreign affairs committee quit in protest.
-- Saleh fires his government on March 20.
-- Senior army commanders say they have switched support to pro-democracy activists. Yemen's representative to the Arab League announces his support for protesters on March 22.
-- Yemeni opposition groups reject Saleh's new offer on March 22 to leave office after organizing parliamentary elections by January 2012. Saleh had earlier said that the country could disintegrate and descend into civil war.