A timeline of how Yemen has plunged from protests to near full-fledged civil war:

January 22: Hundreds of students and other protesters gather at Sana'a University, calling for an end to the 32-year rule of President Ali Abdullah Saleh. The demonstrators were apparently inspired by the protests that led to the ouster of Tunisia's President.

March 1: Tens of thousands of opposition activists demand the ouster of Mr. Saleh. President Saleh fires five of 22 provincial governors, some for criticizing the crackdown on the protests.

March 8: The government deploys military vehicles and extra troops in Sana'a, the capital, as police open fire on protesters, reportedly for the first time, killing at least one person and wounding 80 others.

March 18: As protest crowds swell, security forces fire on protesters in Sana'a, killing at least 52 people and wounding more than 100. President Saleh declares a state of emergency. World leaders criticize the crackdown.

March 20-21: President Saleh dismisses his entire Cabinet. Some senior military commanders join the protesters calling for the president's ouster.

April 2-3: Yemen's opposition leaders urge President Saleh to hand over power to Vice President Abd al-Rab Mansur al-Hadi. He refuses. Rival demonstrators clash throughout the country.

April 5-8: President Saleh accepts an invitation from the six-nation Gulf Cooperation Council (GCC) to hold talks in Saudi Arabia with opposition representatives.

April 10-11: GCC foreign ministers urge President Saleh to transfer his powers to his vice president. Mr. Saleh welcomes the proposal, but does not specify a timeline for stepping down.

April 14-15: Opposition leaders give Mr. Saleh a two-week deadline to resign. More religious and tribal leaders side with the protesters.

April 17-18: Hundreds of thousands of people demonstrate across Yemen, despite facing live ammunition from government forces. An opposition delegation headed by former foreign minister Mohammed Basindwa meets with Gulf Arab mediators in Saudi Arabia to lay out conditions for entering formal talks. The effort is unsuccessful.

April 19: The U.N. Security Council meets on Yemen for the first time since the protests erupted in January. Russia and China reportedly prevent the council from publicly endorsing a draft statement calling on the parties in Yemen to “exercise restraint and enter a dialogue.”

April 21-25: The GCC presents President Saleh with a plan for ending the political impasse and unrest. The plan calls for Mr. Saleh to resign within a month and for a presidential election two months later.

April 30-May 1: Yemen's main opposition coalition accuses President Saleh of refusing to sign the Gulf agreement. Mr. Saleh says he will sign as the leader of the ruling General People's Congress party but not in his capacity as president, as required by the plan.

May 15: Yemen's main opposition coalition says the GCC plan to end the country's political crisis is “dead.”

May 21-22: Yemen's opposition says it has signed a Gulf-brokered deal that would see President Saleh's transfer of power within a month. Mr. Saleh denounces the proposed deal as a “coup.”

May 23-26: Deadly gun battles break out in Sana'a between Yemeni security forces and forces loyal to tribal leader Sheikh Sadiq al-Ahmar. The opposition tribesmen take control of several government buildings.

May 27: Opposition tribal leaders say they are talking with the government and that a cease-fire is in effect, temporarily halting most of the fighting with security forces. International calls continue from several world powers calling for Mr. Saleh to leave office soon.

June 3: President Saleh and five other Yemeni officials are wounded in a rocket attack on the presidential compound in Sana'a.

June 4: President Saleh's forces and forces loyal to tribal leader Sheikh Sadiq al-Ahmar accept a Saudi-brokered cease-fire. A truce negotiated a week earlier quickly deteriorated. Mr. Saleh flies to Saudi Arabia for treatment. Vice President Abd Rabbo Mansour Hadi takes over.

June 5: There are celebrations in Yemen's capital, Sana'a, after word spreads that President Saleh left the country.