Pakistan has had a chequered political history. It has alternated between military and civilian regimes, with the military exercising its influence even when not in power.

The country is run under the 1973 constitution, which established a parliamentary system, with the prime minister at the top, and a federal state structure comprising four provinces.

But amendments introduced by former military ruler Gen Ziaul Haq in 1985, gave the president discretionary powers to appoint services chiefs and sack elected governments and parliaments.

This arrangement has been a source of political instability. Between 1988-97, successive presidents dismissed four elected governments.