In a resounding challenge to the Egyptian military's authority, President Mohammed Morsi ordered Field Marshal Mohamad Hussein Tantawi to step down Sunday.

The order marks a new escalation of an ongoing power struggle between the newly empowered Muslim Brotherhood and the Supreme Council of the Armed Forces, the military council that ruled Egypt after former President Hosni Mubarak's downfall on Feb. 11, 2011. 

Many Egyptians have faulted the SCAF for what appeared to be a slide back into autocracy as the military rulers have responded to protests with violent force, reinstituted laws giving the military sweeping powers of arrest and sought to curb the influence of the newly elected legislature.

Long-repressed Islamist parties like the Muslim Brotherhood quickly emerged as the dominant political force in post-Mubarak Egypt. The Brotherhood's Freedom and Justice Party registered huge gains in parliamentary elections and, in Morsi's election, has an ally serving as Egypt's chief executive.

In addition to dismissing Tantawi and Sami Anan, the army's chief of staff, Morsi nullified a constitutional measure, issued by the SCAF, that sought to enshrine greater autonomy for the SCAF by giving the body ultimate authority over issues related to the military. The declaration would also have allowed Tantawi to remain in his current role until a new constitution is drafted.