A Pentagon-backed Iraqi militia composed mostly of exiles rumbled into town today on the back of U.S. military trucks.

Wearing U.S.-issued uniforms, the fighters waved their weapons. They pumped their arms. They chanted joyfully of their return.

And they were greeted with a cold-eyed indifference that finally silenced them.

As Baghdad showed itself -- revealing blackened streets littered with the debris of lawlessness, dead zones of shuttered stores and, most starkly, a suspicious populace -- the buoyant mood of the 120-man Baghdad Company of the Free Iraqi Forces wilted.

"I wept when I saw the city," said Ahmed Ahmedizzet, a former colonel in deposed president Saddam Hussein's feared intelligence service, the Mukhabarat, and now a colonel in the militia. "But we can rebuild Iraq."

The Free Iraqi Forces (FIF) is the military wing of the Iraqi National Congress, an exile group that elicits both admiration and loathing in Washington.

For the Pentagon, particularly members of its civilian leadership, the group is the seedling of an Iraqi democracy. It is led by Ahmed Chalabi, a longtime opposition leader who on Wednesday came separately to the capital, where he will begin meeting with community leaders, according to his aides. Chalabi's supporters, many of whom see him as Iraq's new president, hope he will rally the people to his agenda of rooting out most remnants of the old order and putting in place a pro-American representative government.

To the State Department and the CIA, Chalabi, a former banker with a fraud conviction in Jordan, is a man of uncertain propriety whose standing among the Iraqi people is questionable. Chalabi takes issue with his conviction in Jordan, which followed the collapse of a bank he ran, saying it was politically motivated.

The FIF represents both an attempt to build an indigenous security force and the opening gambit in a power struggle.

Eager to foster an armed Iraqi presence and build up a replacement for its own troops, the Pentagon flew about 600 FIF fighters and Chalabi to southern Iraq from the northern part of the country last week. Their sudden injection into the field there, ahead of other opposition groups, was a dramatic boost for Chalabi and his organization.

With this deployment, the Pentagon risks incurring the disapproval of other opposition groups who fear that the United States is favoring one faction over another before the mechanism to create an interim authority is in place.

U.S. Special Forces troops, who escorted the FIF fighters into Baghdad today, provided them with seized weapons and some basic military training at an abandoned air defense facility in southern Iraq.

The force will take to the streets of Baghdad Thursday. Its members will work with Americans to help establish security; they hope to use old neighborhood contacts to gather intelligence.

"They are good, capable guys who want to make a difference," said a U.S. Special Forces officer working with the force. "The politics of all this is above my head, but what I've seen I like."

The force has fighters from the major strands of Iraqi society, including Shiite and Sunni Muslims and Kurds. Ahmedizzet, for instance, is Sunni, but most of the force's men, including Chalabi, are Shiite, a community that was brutalized by Hussein's Sunni-led government.

In the impoverished, heavily Shiite towns of southern Iraq, the force received a warm welcome as it dispensed U.S. aid and manned checkpoints. But the real measure of its potential will come in central Iraq, including Baghdad, where Sunnis have traditionally dominated.

Asad Quasi, a militia member, said he fled Baghdad seven years ago, settling in the quasi-independent Kurdish part of northern Iraq after his radical Islamic views put him at odds with the Hussein government. In the north, he said, he shed his old politics and adopted the democratic vision of the Iraqi National Congress.

"We need a natural life, a democratic life, like in any other country," Quasi said. "When I came into Baghdad, I saw the ruins, but I also saw something else: freedom. We can be free."

"Chalabi, Chalabi," shouted some of the fighters today, as onlookers asked who these uniformed men with AK-47s were. But no one took up the chant as people had in towns in the south.

For every smile, and every cheer from the ubiquitous children hoping for a treat tossed from a truck, there were a hundred men and women who just looked and passed on, unimpressed or too busy with the toil of surviving.

"The people don't know who we are," said Ahmedizzet, who fled Iraq in 1998 and settled in Norway after his opposition activities were discovered by the government. "They are afraid. . . . We are going to face many problems here. But we want the people to know we are a part of them and we want all to be part of the new family in Iraq."