When Cairo's central Tahrir Square first erupted in violence on Saturday and a crowd of thousands broke and ran under a barrage of tear gas, the government forces pushing them back were a familiar mix of black-clad riot police and baton-wielding soldiers in fatigues.
The same two-pronged crackdown team has been at work since February, when President Hosni Mubarak stepped down, the military entered the streets, and the Supreme Council of the Armed Forces assumed ultimate political authority.
Riot police and soldiers are often asked to work in sync, and since protests reignited in Cairo, both groups have been seen clubbing the fleeing crowds.
But behind the images of teamwork, the two security forces come from government ministries that analysts say are embroiled in a longstanding power struggle, one which may be exacerbating the ongoing violence.
Central Security Forces
Egyptian riot police are technically known as the Central Security Forces (CSF), a paramilitary unit within the Interior Ministry numbering at least 300,000 men. On paper, their mission is to protect sensitive government sites and subdue civil disturbances.
Formed in 1977, so Egypt would not have to call on the military to quell protests, the ranks of the CSF reportedly grew greatly under Mubarak's regime. Its membership largely consists of military conscripts who failed to meet standards for army service but are allowed to serve their mandatory tour in the CSF.
Relations between the military and CSF have been chilly for years. When thousands of CSF conscripts rioted in 1986 after being told their tours would be extended from three years to four, Mubarak mobilised the army to confront them.
"The army thinks [the CSF] are knuckle-draggers," said Steven Cook, a fellow at the Washington-based Council on Foreign Relations who has researched the Egyptian military. "They think that they are classless and that the military has a more noble mission."
Many Egyptian activists and outside observers believe CSF troops hold a grudge against protesters for seizing Tahrir Square during the first days of the January uprising, forcing the government to withdraw the riot police from the streets.
"There is a clear revenge factor at play among the CSF," said Michael Hanna, a fellow at the New York-based Century Foundation and an Egypt expert.
Yet even so, the Saturday crackdown was a "very strange" tactic, Hanna said. CSF troops used violence to disperse a small group of protesters camping in the square, most of them reportedly the family of the revolution's "martyrs".
"That's a weird choice, to do something so provocative this close to elections," he said. "And the CSF were there by themselves for a long time [without the army], and that begs a lot of questions."
Supreme Council of the Armed Forces
Egypt's military is often called the country's most respected institution, supposedly immune from corrupt politics and still gleaming with what is seen locally as its victory in the 1973 war with Israel.
At times, however, the military has proved inept at handling its power, experts say, and its outdated tactics and rivalry with the Interior Ministry may be exacerbating the violent reaction to renewed protests.
Although the Supreme Council of the Armed Forces (SCAF) holds ultimate executive power in Egypt, it may not be able to control the day-to-day actions of Interior Ministry generals. The ministry's commanders oversee legions of police and CSF and are still accustomed to the free rein given by the Mubarak regime.
"The ability of the military to communicate with other ministries is limited in a direct way because the senior military command doesn't even use email," Cook said. "If there's no one other end to pick up the phone [at the Interior Ministry], the message is not sent. This is a big problem, in that they communicate like it's the 1960s."
Although the military played a brief role in a second sweep of the square on Saturday, it has since taken a back seat to the CSF. On Monday, the SCAF reportedly said it had sent its troops out only after a request for help from the Interior Ministry. The military has since pledged to "protect" the protesters while apologising for the violence and expressing condolences to the family of the dead and the injured.
But Cook said his sources in Egypt told him the military had still been resupplying police with vehicles and equipment during the fighting, though they did not want to be seen "out on the street".
The military in fact may be wary of the Interior Ministry, especially of reforming or purging it of the worst offenders, Hanna said.
"SCAF is quite afraid of security sector reform, because of the threat of retaliation that is sitting right there within the Interior Ministry," Hanna said. "It is alleged to have links to organised crime. There has been an increase in crime since the Interior Ministry has been threatened. I don't think that's a coincidence."
If SCAF were to move to limit the Interior Ministry's power, the police generals, many of whom have maintained their positions since the revolution, could react by instigating a crisis, as they are alleged to have done by opening prisons and organising "thugs" during the 18 days of protest in January and February.
In the meantime, the CSF continue to lead the crackdown, and the SCAF may not be able to reign them in.
Jon Jensen, a journalist who has observed the some of the worst fighting near the square, said riot police had been fighting protesters for two days with nearly constant tear gas barrages and blasts from pellet guns.
Supporting the riot police on Sunday night, Jensen said, was a unit of 50 to 100 troops in military fatigues backed by three armoured personnel carriers.
"They're in defensive posture, trying to protect the Interior Ministry," he said, referring to the CSF headquarters.
The SCAF has been "passive", Cook said, "and I don't think it has worked. The Interior Ministry has these rogue elements who are interested in showing ... everyone else who's boss."
Hanna suggested there is "something like blackmail" occuring between the Interior Ministry and SCAF, but neither he nor others were willing to predict the outcome.
"It's a total black box," he said.