The renegade air force officers marched in the capital clutching banners and chanting, “Get out, get out,” a familiar cry in this country’s year-old uprising. They were not seeking the ouster of President Ali Abdullah Saleh, but rather that of his half brother, who heads the air force.

“We will not give in until the removal of Mohammed Saleh,” the officers shouted.

Yemenis vote Tuesday in a historic election expected to formally end President Saleh’s 33-year rule, but a battle for the armed forces is increasingly taking center stage. Even if the question of presidential succession is resolved peacefully, Saleh’s son, nephews and other relatives remain in firm control of influential positions in the military and security forces.

Of all the divisions plaguing this impoverished yet strategic Middle Eastern nation, the rifts in the military are among the most significant. Opposition politicians, street activists and Western diplomats say that as long as Saleh’s family remains powerful, so, too, will Saleh. And that will mean little real change, they say, for a nation struggling with al-Qaeda militants, a southern secessionist movement, and intensifying tribal and regional rivalries.

“In our point of view, the president’s relatives in the military and security institutions are the main obstacle to any improvement after Saleh is gone,” said Maizar al-Junaid, 32, a youth activist leader. “They have to be removed, and Yemen must build a new unified army.”

Yemen’s military has been divided since March 18, when snipers loyal to the president killed more than 50 protesters. Gen. Ali Mohsen al-Ahmar, Yemen’s most powerful military leader and a key Saleh ally, then declared his allegiance to the revolt; other high-level figures in the government, military and influential tribes soon defected as well.

Since then, Mohsen’s 1st Armored Division has protected protesters and clashed with the Republican Guard, led by Saleh’s son, as well as the central security forces, led by Saleh’s nephew. The factions have carved up the capital, taking over Sanaa’s streets and neighborhoods, erecting checkpoints and berms.

According to the terms of a U.S.-backed power-transfer deal, Vice President Abed Rabbo Mansour Hadi will succeed Saleh, who is in the United States receiving medical treatment. Both the ruling party and the opposition agreed that Hadi was their choice to run Yemen during a transitional period of at least two years. His name is the only one on the ballot.

One of Hadi’s key tasks will be to reunify the army. A military committee has been created to perform this task, as well as remove the armed forces from the capital. But, so far, it has not succeeded. The forces loyal to Mohsen and to Saleh’s family remain in their positions, mistrustful of each other.

In another part of Sanaa, Yemen’s most influential tribal family, which also broke away from Saleh, exerts control.

Hassan Zaid, an opposition leader, said the air force demonstrations show that Saleh and his family “are losing control.” But he stressed that it was not necessary to remove Saleh’s relatives from their military positions, provided they follow the orders of the new unity government.

“If they remove the son and nephews, it will be in whose interest?” Zaid said. “The balance will now be in the favor of Ali Mohsen, who we know wants to control the power.”

His comments underscored the widening of Yemen’s political divisions as Saleh’s presidency appears to be nearing a close. Senior ruling-party officials have accused Mohsen, the Ahmar clan and al-Islah, the country’s most powerful opposition party, of orchestrating the air force demonstrations, which began late last month. They said they would prevent any attempt to oust Mohammed Saleh from his position.

“If the state gives in to their demand, this will spread throughout all the military, and chaos will spread,” said Abdu al-Janadi, the deputy information minister. “This is a political demand, and the armed forces should not be politically affected.”

“Islah wants to take over power,” he added.

Mohammed al-Saadi, the deputy leader of Islah, denied the allegations. He said the president’s son, nephews and relatives have no future in the armed forces. If they decide to remain, he said, they would serve as mere officers and would have to obey orders.

“Or they would have to leave,” Saadi said. “And this second option is the most probable one.”

At the demonstration, none of the air force officers appeared to be thinking about politics. Their demands included pay raises and promotions. But their chief demand was the removal of the president’s half brother. A year ago, their actions would have meant a death sentence.

“Mohammed Saleh is unfair. He’s corrupt,” said Col. Mohad Dahan, 60. “He stole the money of his forces. He made his forces beg on the street for the past 22 years.”

Dozens of his comrades who were gathered around him nodded in agreement.

On a nearby air force base, where many of the protesters worked, Gen. Muhsin Ali Matash, 51, dismissed the demonstrations as the actions of a few disgruntled officers. He blamed the protests on “political forces that want to harm the country.”

To remove the air force chief requires a presidential order from Hadi, Matash said. Hadi is a military man who views Mohammed Saleh “like a brother,” he said.

“We don’t think he’ll be removed because of these people,” Matash said with a smile.