During the 1950s and especially the 1960s, tension developed and escalated between East and West Pakistan, which had many differences in language and culture although both were majority Muslim. East Pakistan had a majority of Pakistan's population and economic activity but Pakistan's government and military were largely dominated by the upper classes from the west. Friction first developed over use of Bengali language then political autonomy for the East, and the perceived poor response of the government to a massive cyclone killing up to half a million people in East Pakistan.