The new defence minister, a former director of military intelligence and reconnaissance, has an air of the unknown about him.
Officials close to President Mohamed Morsi said the president wanted to secure the army behind him amid threats of protests from former regime loyalists, who promptly denounced his new defence minister.
The appointment of al-Sisi and the sacking of General Hussein Tantawi appeared to be the last word in an unsubtle power struggle between the army and Egypt's first civilian and Islamist president.
One of al-Sisi's few public comments has been his support for virginity tests imposed by the military on female protestors arrested at Tahrir Square, which were later ruled illegal by a Cairo court.
Al-Sisi commanded a mechanised infantry battalion before rising through the ranks and heading the military intelligence apparatus.
He is believed to have been favoured by Tantawi, and will continue to exert the military's influence over state affairs, particularly economic and foreign relations.