The night of June 25, 2012, fireworks burst over Cairo as crowds danced in the streets and celebrated the victory of Egypt’s new president, Mohamed Morsi. Supporters flooded Tahrir Square, some chanting, “Morsi, Morsi! Down, down with military rule!” Congratulations poured in from around the world—David Cameron, Barack Obama, and the leaders of Egypt’s Coptic Church called Morsi’s election a landmark victory for democracy in the Middle East.

One year on, the mood in Cairo is far darker. On Sunday, massive anti-Morsi protests are planned for the anniversary of his inauguration. Millions are expected to turn out across the country, and clashes between demonstrators and riot police seem inevitable. Worse, many analysts—and even the protest’s own organizers—expect fighting to erupt between Morsi’s opponents and his Islamist supporters. Activists like Hazem el-Zohery, a key organizer of the upcoming protests, now say they want Morsi gone at any cost—even if that means the country’s powerful military stepping back in to take his place.

Zohery, 38, is one of the co-founders of an aggressive new campaign that is presenting the president with his greatest challenge to date. Named Tamarod, or ‘Rebel,’ it started off as an anti-Morsi signature drive this spring calling for early elections. But the group’s numbers quickly swelled with more than 15 million people signing the petition, according to Tamarod’s leaders. Tamarod plans to flex that muscle on the streets this weekend, leading calls to protest backed by the country’s political opposition. “We are proving to [Morsi] that, no, the people are not with you,” Zohery says.

“We are not afraid of violence,” adds fellow Tamarod co-founder Mahmoud Badr.

Protesters will demand Morsi’s resignation, and Zohery hopes their numbers can convince him to step down—an extremely unlikely prospect, analysts say. But Zohery says he’d also consider it a “success” if the military removed Morsi instead. “The Army is called the Egyptian Army. It is not Morsi’s army,” Zohery says, adding that the military could follow Morsi’s removal with a transition plan for new elections. “In the end, the Army is with the people."

Morsi and his backers, for their part, appear to be bracing for a fight. Following a weekend in which Islamists staged a mass rally in Cairo widely seen as a preemptive show of force—some Islamist youth even put on a martial arts display—Morsi addressed the nation in a defiant speech Wednesday night in which he denounced figures he sees as part of a conspiracy against him. “Some dream of the return of the old regime,” Morsi said.

One of the figures Morsi named was Mohamed al-Amin, the wealthy owner of a TV channel that airs a popular satirical talk show that targets Morsi frequently. On Thursday, Amin was accused of tax evasion and banned from leaving the country. Bassem Youssef, the satirical talk show's host, has already found himself in the legal crosshairs in recent months. Such heavy-handed tactics have only fueled critics who accuse Morsi of taking on an authoritarian governing style.

While Tamarod’s numbers should be taken with “a big grain of salt,” cautions Eric Trager, an Egypt specialist at the Washington Institute for Near East Policy, Morsi’s government and supporters have appeared increasingly agitated by the prospect of the coming protests. And some protest organizers seem to be calculating that if the streets explode with unrest, the Army may be forced to step in to quell the chaos. “They want to use violence as a way to get the military involved,” Trager says.

The military, Trager adds, appears hesitant to intervene. It ran the country after Morsi’s predecessor, Hosni Mubarak, was ousted in the Arab Spring—and saw widespread protests against its rule, that were backed by many of the same people now calling for Morsi to step down. “They don’t want to come back. They have no interest in [ruling Egypt]. They’re not good at it,” Trager says. “They like an arrangement where they can have influence behind the scenes. But they have a responsibility when things get out of hand. The question is, will things get out of hand?”

In last year’s election, as he faced down a candidate widely considered a vestige of the old regime, Morsi—a former senior official in the Muslim Brotherhood—received critical support from many of the liberal and secular activists now opposing him. But the country quickly polarized. Morsi’s critics accuse him of concentrating power in the hands of his Islamist allies and pushing for religious rule. His backers, meanwhile, claim they’re fending off counter-revolution. Violence between the two sides erupted late last year, after Morsi temporarily granted himself near-dictatorial powers to help an Islamist-dominated assembly draft a new constitution. Demonstrators camped outside the presidential palace were attacked by Morsi’s supporters, setting off a night of deadly street clashes.

Tensions have boiled since, with pro- and anti-Morsi crowds occasionally clashing violently. The military has so far proved unwilling to mediate, and Morsi’s allies insist that the Army tacitly backs their side. In a rare statement on the growing unrest, Gen. Abdel-Fattah el-Sissi said the military will act if necessary to prevent Egypt from entering a “dark tunnel of conflict [and] internal fighting.”

“Those who think that we are oblivious to the dangers that threaten the Egyptian state are mistaken,“ Sissi warned. “It is not honorable that we remain silent in the face of the terrorizing and scaring of our Egyptian compatriots. There is more honor in death than watching a single Egyptian harmed while the army is standing idly by.”

The Army fortified its positions around major cities on Wednesday in anticipation of the weekend’s protests. “They likely already feel there will be a good chance they will need to step in,” says Paul Sullivan, an expert on Middle East security issues at Georgetown University. “This is an explosive moment.”

Zohery, the Tamarod leader, says he would consider it a “success” if the Army were to remove Morsi from power. In that event, he says, it could hand the reins to the country’s Supreme Court, which would then oversee a transition plan. “The Army is called the Egyptian Army. It is not called Morsi’s Army. It is for protecting the people,” he says.

Many anti-Morsi activists are wary of the potential for military action—and angered by the fact that some of their compatriots seem to be promoting the idea. “Now if you dare to speak that you are against military rule and want real democracy, you will be accused of being a traitor and [Muslim Brotherhood] agent,” tweeted the well-known liberal activist who goes by the handle Zeinobia in frustration earlier this week.

No matter how many people take to the streets, Morsi is unlikely to step down on his own. He stood firm during his address to the nation this week, even as he admitted to some “mistakes” during his first year in office. “The enemies of Egypt have not spared effort in trying to sabotage the democratic experience,” he said.

Morsi’s Islamist supporters, who say the opposition should wait three years until the next voting cycle and try to effect change through the ballot box, are angered by what they see as an underhanded attempt to unseat their elected standard-bearer. And they’ve long made it clear that they will not hesitate to respond with force if the presidency seems under real threat. “The Muslim Brotherhood is steeling for a fight,” says Trager, of the Washington Institute for Near East Policy. “The rank and file are really pushing their leaders for a command to go and respond.”

The country’s more hard-line Islamist groups, meanwhile, are falling into line behind Morsi. “When the other side starts violence, the Islamists will respond,” says Assem Abdel Majed, a leading member of Gamaa Islamiya, the former terror group.

Zohery and his colleagues know they are playing a dangerous game, but say they see no alternatives. “If we want to make real change for the country, then we’re moving this way,” Zohery says. The revolution against Mubarak, he adds, was itself a “dangerous move.”

With Maged Atef in Cairo.