Tens of thousands of Egyptians returned to protest in Tahrir Square Friday, signaling their growing impatience and dissatisfaction with the military officers who have ruled the nation since former President Hosni Mubarak was forced from power in February by a popular uprising.

In what was dubbed a “Day of Cleansing,” protesters filled the square to demand that Mr. Mubarak be put on trial, and express their anger that former officials suspected of corruption had not yet been brought to justice. They directed chants toward Field Marshal Mohamed Hussein Tantawi, who leads the military council temporarily in charge of Egypt, urging him to act. One woman stood silently wearing a sign addressed to Tantawi that read, “Are you with us or against us?”

Such open questioning of the military is a marked departure from the early days of the movement, when Egyptians showered the Army with flowers and saw them as defenders of the people after tanks rolled into the streets to restore order after violent clashes with police. That goodwill, which lasted even after the Army stood silently by while government-paid thugs attacked peaceful protesters, has begun to fray. Some Egyptians now wonder if Mr. Tantawi, Mubarak’s long-time defense minister, is shielding his former boss from prosecution.

“Tantawi was Mubarak’s man,” said Yasmine Said as she held a flowered umbrella to shield herself from the warm sun in Tahrir. “Mubarak is sitting in a villa in Sharm El Sheikh ordering delivery, while here nothing has changed. We want him to face justice. That’s it.”

Mock trial for Mubarak

Protesters held a mock trial for Mubarak while others carried caricatures of top former regime officials behind bars. Though he has not yet been charged, Mubarak and his son Gamal, who held a top post in Mubarak’s National Democratic Party, will be questioned on corruption charges. Mubarak and his family are under house arrest and his assets have been frozen. His former chief of staff was detained for questioning this week, and several other top regime officials have been detained.

About 10 officers in uniform joined the protest in Tahrir, despite a warning from the military that any soldiers who did so would face an immediate military tribunal. In the past week, several Egyptians who said they were former military officers posted videos critical of the military on YouTube and urged soldiers to join the protests Friday. It was unclear exactly who the officers in Tahrir were and whether they were current or former members of the military. But as they stood on the stage, the crowd chanted “The people want the field marshal to fall!”

A small group of liberal secular protesters has vocally criticized the Army since it violently cleared protesters from Tahrir last month, severely beating many of them. And hundreds to thousands of people have been detained by the Army and tried in military courts without access to civilian lawyers. Yet until recently, such criticism of the Army had not been widespread.

Muslim Brotherhood's role

The large turnout Friday was partially due to support from the Muslim Brotherhood, Egypt’s most organized political movement. Since the military council gave in to protesters demands by firing the cabinet ministers associated with Mubarak, the Brotherhood has refrained from calling for protests, and has been seen as supportive of the military council. It backed the council's proposed constitutional amendments, which many of the secular liberal protesters rejected. The amendments were approved in a national referendum with 77 percent of the vote.

The group’s reversal Friday in calling for a protest was seen by some as an move to place pressure on the Army. But Ibrahim el-Houdaiby, a former member of the Brotherhood, says it was simply an attempt to capitalize on the popular sentiment of growing discontent, after a protest last week drew large numbers.

“I think they don’t want to seem isolated or detached from the people,” he says.

The landscape in Tahrir Friday was a reflection of the fractured political scene in Egypt as it gears up for the first free parliamentary elections in September, the first in half a century. At least half a dozen stages were set up throughout the square, each with its own loudspeaker system, blasting music or political speeches that were partially drowned out by the neighboring stage. As protesters wandered by, many were unaware of who was actually on most of the smaller stages.