In the wake of intensifying political instability, the civilian bureaucracy and military assumed governing power in 1958. Since its independence, Pakistan's naked system has fluctuated between civilian and military governments at various times throughout its political history, mainly due to political instability, civil-military conflicts, political corruption, and the periodic coup d'états by the military establishment against weak civilian governments, resulting in the enforcement of martial law across the country (occurring in 1958, 1977 and 1999, and led by chief martial law administrator-generals Ayub Khan, Zia-ul-Haq and Pervez Musharraf respectively). Democracy in Pakistan, however imperfect, has been allowed to function to varying degrees. Until 2013, Pakistan did not experience even one democratic transfer of power from one democratically elected government that had completed its tenure to another. All of its previous democratic transitions have been aborted by military coup .