CAIRO -- The world's most influential Islamist movement is in danger of collapse in the land of its birth -- its leaders imprisoned, its supporters slain and its activists branded as terrorists in what many are describing as the worst crisis to confront Egypt's 85-year-old Muslim Brotherhood.
Mohammed Badie, who has headed the Brotherhood's Egyptian branch since 2010 and is its "spiritual guide," was interrogated and remanded into pretrial detention Tuesday on a variety of charges, including inciting the killing of protesters outside the Brotherhood's Cairo headquarters in June. He is also accused of possessing arms, running an illegal gang and assaulting the military. He is to go on trial with two other Brotherhood leaders this month.
In the week since Egypt's new military-backed rulers ordered a brutal crackdown on camps filled with protesters calling for the reinstatement of ousted President Mohammed Morsi, the group that used its organizational muscle to win the country's first democratic elections, held in late 2011 and early 2012, has been cast into disarray.
Analysts worry that its members, bitter and angry after the deaths of more than 1,000 of their supporters in the past week, could abandon the Brotherhood's decadeslong commitment to nonviolence, particularly as its leadership loses its grip on them. Some pro-Morsi demonstrators have been spotted with weapons, and attacks against security forces in the volatile Sinai Peninsula have intensified since Mr. Morsi was deposed July 3.
Meanwhile, the movement is battling a level of popular hostility perhaps unprecedented in its history. The Brotherhood's strategy of confronting the government with sit-ins and marches in recent weeks seems to have only inflamed public opinion.
On Tuesday, Brotherhood supporters vowed that they would not resort to violence as they continued to challenge the interim government installed by the military after Mr. Morsi, the group's standard-bearer, was toppled. "Our only option is the peaceful method," Khaled Hanafi, secretary-general of the Brotherhood's Freedom and Justice Party, told journalists at a Cairo news conference Tuesday.
The detention overnight of the Brotherhood's Mr. Badie would not change the group's approach, he said. "We regret the arrest of Dr. Badie, but we have chosen a path, and regardless of the sacrifices, we must continue," Mr. Hanafi said.
The detention of the Islamist movement's spiritual leader seemed to complete the humiliation of the Brotherhood's leadership. The mass arrests and deaths of its officials have left the group splintered and unable to take coordinated action, analysts say.
Throughout its history, the Brotherhood has repeatedly clashed with Egypt's authoritarian governments. But what's different now, analysts say, is that it is battling not only a military-backed government, but also the disdain of a broad swath of society. Many Egyptians are irate at Mr. Morsi for the country's economic slide and the rise in crime during his one-year rule. Others complain that the Brotherhood tried to grab power by excluding minority political groups and trying to insulate their decisions from judicial review.
It is not only the current leadership that is being decimated, but also, potentially, the future ranks. Among those who have died in the crackdown are Mr. Badie's 38-year-old son, the 17-year-old daughter of Freedom and Justice party leader Mohammed Beltagy, and Khaled al-Banna, grandson of the Brotherhood's founder, Hassan al-Banna. All were shot by security forces over the past week.
The fragmentation could have far-reaching consequences, for instance, if the government eventually wants to negotiate with the group. Ibrahim el-Houdaiby, a political analyst who belongs to a prominent Muslim Brotherhood family but left the organization in recent years, said the government, by trying to destroy the Brotherhood's leadership, may no longer have a negotiating partner that can keep the group's followers in line. He said the Brotherhood is already losing control over them. "It will lose a great part of its members to violent movements," he said.
With Egypt becoming increasingly polarized, the Brotherhood's opponents are cheering the group's possible demise. On Tuesday, the headline in the liberal Tahrir newspaper, named for the revolution that unfolded two years ago in Cairo's central Tahrir Square, trumpeted: "The End of the Brotherhood."
The Tamarod (rebel) movement, which led the massive street demonstrations that culminated in the coup that toppled Mr. Morsi, on Tuesday repeated its call to ban the Brotherhood.
Brotherhood figures are not the only ones in the cross hairs, however. Also Tuesday, a lawsuit was filed against Mohamed ElBaradei, who briefly served as Egypt's vice president after Mr. Morsi's ouster before resigning in protest at the bloodshed last week and leaving the country.
The case was brought by an Egyptian professor, who accused him of "betrayal of trust" for quitting his post.