A chronology of key events in Pakistan's history:
—Aug. 14, 1947: Pakistan is founded when British rule over the region ends and the Asian subcontinent is partitioned into Islamic Pakistan, divided into East and West, and predominantly Hindu India.
—Sept. 11, 1948: Pakistan founder Muhammad Ali Jinnah dies.
—Oct. 16, 1951: Pakistan's first prime minister, Liaquat Ali Khan, assassinated in gun attack, triggering political instability.
—Oct. 27, 1958: Pakistani army chief Mohammed Ayub Khan seizes power.
—March 25, 1969: After months of opposition rioting in West and East Pakistan, Mohammed Ayub Khan hands over power to army chief Gen. Yahya Khan.
—Dec. 7, 1970: East Pakistan-based Awami League wins general elections. In response, Yahya Khan suspends the government, triggering widespread rioting in East Pakistan. Civil war breaks out in the wake of army action.
—Dec. 16, 1971: Pakistan troops surrender in East Pakistan after India's intervention in the civil war. East Pakistan becomes independent Bangladesh.
—Dec. 20, 1971: Yahya Khan resigns, Zulfikar Ali Bhutto becomes president. A parliamentary system of government is adopted later, and Bhutto becomes prime minister.
—July 5, 1977: Pakistani army chief Gen. Mohammed Zia ul-Haq seizes power.
—April 4, 1979: Bhutto hanged after Supreme Court upholds his death sentence on charges of conspiracy to murder and Zia rejects his mercy petition.
—Aug. 17, 1988: Zia dies in a mysterious plane crash.
—Dec. 2, 1988: Bhutto's daughter Benazir becomes Pakistan's first woman prime minister.
—Aug. 6, 1990: Ms. Bhutto's government dismissed amid charges of corruption and mismanagement.
—Nov. 1, 1990: Nawaz Sharif becomes prime minister following election.
—April 18, 1993: President Ghulam Ishaq Khan dismisses Sharif's government on corruption charges but the Supreme Court revokes the order and reinstates Sharif.
—July 18, 1993: Due to serious differences between President Khan and Prime Minister Sharif, then-army chief Gen. Waheed Kakar forces both to resign.
—Oct. 19, 1993: Ms. Bhutto becomes prime minister for a second time following elections.
—Nov. 5, 1996: Ms. Bhutto again dismissed amid renewed charges of corruption and incompetence by her own party president Farooq Leghari.
—Feb. 17, 1997: Sharif becomes prime minister for a second time after elections. Ms. Bhutto goes into self-imposed exile to avoid prosecution in corruption cases.
—Oct. 12, 1999: Army chief Gen. Pervez Musharraf ousts Sharif in a bloodless coup after the prime minister tries to sack the general. Sharif exiled after court convicts him of conspiracy against Musharraf.
—Nov. 21, 2002: Zafarullah Jamali becomes prime minister after pro-Musharraf parties win election.
—Aug. 23, 2004 Shaukat Aziz elected prime minister after Jamali resigns due to differences with Musharraf.
—Oct. 5, 2007: Musharraf issues a controversial ordinance protecting officials from past corruption charges as part of a deal that paves the way for Ms. Bhutto and Sharif to return home.
—Oct. 18, 2007: Ms. Bhutto returns to the country from exile to participate in elections.
—Nov. 3, 2007: Musharraf declares state of emergency and sacks the chief justice of the Supreme Court, trigger a nationwide protest movement led by lawyers that weakens his grip on power.
— Nov. 25, 2007: Sharif returns home from exile.
—Dec. 27, 2007: Ms. Bhutto assassinated in a gun and bomb attack.
—March 25, 2008: Yousuf Raza Gilani becomes prime minister after the Pakistan People's Party wins election on the back of sympathy over Ms. Bhutto's death.
—Aug. 18, 2008: Musharraf resigns from presidency under pressure from main political parties.
—Sept. 6, 2008: Ms. Bhutto's husband, Asif Ali Zardari, elected president.
—June 19, 2012: Supreme Court disqualifies Prime Minister Gilani for refusing to reopen old corruption case against the president.
—June 22, 2012: Raja Pervez Ashraf becomes prime minister.
—March 16, 2013: Pakistan People's Party government reaches historic milestone by completing its full five-year term.
—March 24, 2013: Mir Hazar Khan Khoso appointed as caretaker prime minister.
—May 11, 2013: Elections will mark the first time a civilian government has completed its full five-year term and transferred power in democratic elections.