King Hamad of Bahrain has appointed his son, Crown Prince Sheikh Salman bin Hamad al-Khalifa, as deputy commander-in-chief of the army.
The move cements the royal family's control of the armed forces, of which the king is the supreme commander.
King Hamad also removed Sheikh Khalifa bin Ahmad al-Khalifa as defence minister.
A royal decree said defence matters had been placed under the control of the state minister for defence affairs.
The decree did not say how long the minister of state, Sheikh Mohammad bin Abdullah al-Khalifa, would act in the place of the minister.
Sheikh Salman would "oversee the implementation of public policy and the military, administrative, economic and financial affairs of the Bahrain Defence Force and the National Guard, in addition to other authorities entrusted to him by the supreme commander", the decree said.