The Muslim Brotherhood (known in Arabic as al-Ikhwan al-Muslimeen) is Egypt's oldest and largest Islamist organization. Founded in 1928 by Hasan al-Banna, it is widely considered the world's most influential Islamist organization, with numerous branches and affiliates. It is "the mother of all Islamist movements," says Shadi Hamid, a Middle East expert at the Brookings Institution's Doha Center. The group has emerged as Egypt's biggest opposition movement. Many analysts expect the Brotherhood to play a larger role in the country's future, following the anti-government protests of 2011 in which hundreds of thousands of Egyptians took to the streets to call...