SANA, Yemen — Abu Raad strutted through the streets of the Yemeni capital as if he owned them. His obvious glee, at a time of crisis in the country, bordered on naïveté. But he had his reasons to be happy.

Growing up as a Houthi in the northern province of Saada, he experienced years of war and brutality while fighting for the rights of his Zaydi sect, an offshoot of Shiite Islam, against the government. He described being tortured by military captors who dragged his clutched fists over splintered wood, pushing the sharp pieces under his nails. He was a teenager then.

But now, he was the one in power, embraced by many of the uniformed men who once gave their allegiance to the state.

“We are in this together,” said Abu Raad, 21, who refused to give his real name for security reasons. He pointed to Fathi Ali, a soldier standing guard outside Parliament, saying that Mr. Ali had spent 30 years in Yemen’s armed forces without being promoted beyond the rank of soldier.

“Yes, so far, we are in this together,” Mr. Ali, a Sunni, repeated.

Once a party representing the insular demands of the Zaydis, who account for about a third of the country’s 26 million people, the Houthis see themselves now as having evolved into a broad-based voice against government oppression, corruption and incompetence.

How successful the Houthis will be in unifying the country or overcoming sectarian tensions remains to be seen. Long divided between north and south, Yemen was unified only in 1990, and is now facing rising calls from separatists in the south, which is also where Al Qaeda in the Arabian Peninsula is anchored.

For now, however, the Houthis are wrapped in the warm glow of victory, where all seems possible.

With backing from Tehran, they leapt to power in the fall, when their militants swept into Sana, the Yemeni capital, taking control of key installations and establishing themselves as the dominant force on the ground. Last week, they besieged the presidential palace and dictated demands for more influence, a step that led the United States-backed president, Abdu Rabbu Mansour Hadi, to resign.

That, apparently, has led Washington to engage the Houthis on security issues, at least, and some political matters as well, as a State Department spokesman made clear on Wednesday.

“As a participant in discussions about Yemen’s political direction,” said the spokesman, Edgar Vasquez, “the Houthis will have many reasons to talk with the international community.” Such reasons, he added, include security assurances for diplomats and articulating how they plan to move forward as part of a transition process in Yemen.”

The cooperation extends even to military matters, a senior American military official said. “I’ve got no details on the mechanics,” the official said. “But I understand there are some indirect communications, nothing official. Just need to deconflict and not bump into each other as we go after A.Q.A.P.,” a reference to Al Qaeda in the Arabian Peninsula.

But as party leaders continue to battle and bargain behind tall walls, young men like Abu Raad are inadvertently becoming part of a new reality shaping itself on the ground, turning many of their contemporaries into rebels with a cause, a gun and a job.

After months of fighting, Abu Raad is now responsible for training new recruits. He circulates among the Houthi patrol units, called popular committees, that are sprinkled through the city to keep a sense of order and consolidate control. Young men manning the units often stand guard in their neighborhoods. Most of them are Zaydis, but new to the Houthi movement.

“I tell them to smile,” Abu Raad said, explaining that the new generation does not share the tumultuous past that has taught the fighters from the north to remain patient and responsible.

As the group has expanded its ranks and grown more powerful, self-appointed men of all ages and backgrounds have come to run the city with uncontested authority. Some showed purposeful humility, addressing drivers and pedestrians politely, but others recklessly raced the army trucks they appropriated down busy streets.

Treating their enemies with respect was an early tactic, designed to win the support of tribes that had sided with the state and fought them. “When we captured an injured enemy at war, we made sure to treat him before we let him go,” Abu Raad said.

These were the teachings of Hussein Badreddin al-Houthi, who is the brother of the movement’s current leader, Abdel Malik al-Houthi. He charted a more radical course to combat the spreading influence of an ultraconservative Saudi-style Sunni Islam and seek greater rights for his minority.

It was Hussein Badreddin al-Houthi, inspired by the fiery rhetoric of the Iranian revolution and the politics of Hezbollah, who came up with the group’s deceptively pugnacious slogan: “God is great, death to America, death to Israel, damnation to the Jews, victory to Islam.”

The Houthis called it al sarkha, or the scream. On the face of it, there is contempt for the West, but at its heart is an implicit rejection of United States-backed Arab dictators, whom they see as weak and treacherous. Ali Abdullah Saleh, Yemen’s longtime president, understood this and plotted to contain the Houthis, until he was driven from power in 2012 by the wave of Arab Spring revolutions. (The two former adversaries are now in an uneasy alliance.)

“We are the sons of the revolution,” said Muhammed al-Madari, leaning against an army truck. Mr. Madari, 21, was standing with a group of men patrolling a street lined with key government and commercial buildings in downtown Sana.

He wore a green camouflage jacket and brown camouflage pants, his head wrapped in a camel scarf with his jet-black hair peeping out from the front. He clutched a Chinese-made Kalashnikov rifle, which, in the current atmosphere of relative quiet, looked more like an accessory than a lethal weapon.

“We are Ansar Allah,” or Champions of God, he emphasized, invoking the newer and more popular name for the Houthi rebel movement.

For many in Yemen, the revolution brought a momentary sense of freedom. For the Houthis, it was the critical juncture where they say they transformed from an insurgent group with a grudge to a movement that is reaching out to, and now drawing more support or at least acceptance from, the country’s Sunni majority. It is also when they began referring to themselves as Ansar Allah, rather than Houthis, casting the movement in a new light.

“They used to call us the enemies of Allah,” said another member of Mr. Madari’s unit, who goes by the nom de guerre Abu Ali. He was sitting behind the steering wheel, chewing on khat leaves, a mild narcotic that induces a sense of euphoria. It was Friday afternoon, the first day of the Muslim weekend, and he had started to relax earlier than usual.

“But now more people have gotten to know us,” he said, turning to look at an 18-year-old man next to him in the passenger seat. He was more reclusive and refused to give his name, but he said he was raised in a village on the outskirts of Sana in an ultraconservative Salafi Sunni family that had recently come under the fold of Ansar Allah.

In a country where more than half the population lives on less than $2 a day, the group has extended its reach into more needy areas, building a safety net and slowly introducing people to its political principles and faith.

Abu Ali, who is a colonel in the armed forces, said he seized the army vehicle himself and was now using it to extract concessions from the state.

In September, the Houthis successfully pushed back against a government plan to reduce fuel subsidies, earning them added credibility.

“I swore allegiance to God, to the country and to the revolution, not to any specific leader,” he said. “The revolution started in 2011, but the real revolution is this one.”

As he made his rounds, Abu Raad stopped at a charming, but dilapidated building. The sign in front said it was a museum, long abandoned by the state, it appeared. The Houthis were using it as an office.

They placed a couple of concrete barricades, painted in their green color, in front of the entrance.

“We are going to give it back,” Abu Raad said. “Look, we never removed the sign. We want it to be a real museum.”

The New York Times