Tunisian army chief Rachid Ammar leaves his post after announcing his retirement on June 24.
The move comes amid increased political tensions in connection with the country's democratic transition.
"I decided to leave the service under the age limit .. I asked the president on Saturday and he agreed to my departure," said Ammar.
Public support for democracy activist Ammar weakened after he was accused of playing a role in the extradition of Muammar Gaddafi's prime minister, Baghadi al-Mahmoudi, to Libya.