Members of Saraya al-Salam (Peace Brigades), a group formed by Iraqi Shiite Muslim cleric Moqtada al-Sadr, prepare to reinforce the government, seeking to reclaim Fallujah. (Haidar Hamdani/AFP/Getty Images)

The Iraqi military on Sunday said it is planning to storm Islamic State-held Fallujah, the city that was the scene of the bloodiest fighting for U.S. Marines during the Iraq War.

In a late-night televised address, Iraqi Prime Minister Haider al-
Abadi said the operation to retake the city in the western province of Anbar had begun.

A statement from the military said counterterrorism forces, police, tribal fighters and popular mobilization units — which include an array of Shiite militias — will be involved. U.S.-supplied F-16 jets already have begun bombing targets in the city, the statement said. Civilians were urged to stay away from Islamic State headquarters.

Few expect an easy fight. Islamic State militants have dug in and built defenses in the city since capturing it more than two years ago, the first in the country to fall to the extremist group. Fallujah has long been considered a hotbed of rebellion and extremism, with even the heavy-handed Saddam Hussein struggling to control its tribes. U.S. Marines fought Sunni insurgents during two battles for the city in 2004, the second of which marked the heaviest urban combat for U.S. troops since the Vietnam War, killing nearly 100 service members.

It’s not an order of battle that correlates to U.S. military policy, which had focused on an offensive targeting Mosul, the Islamic State-held city farther north. President Obama has said he expects the recapture of Mosul to be close to complete by the end of the year. But a drawn-out battle for Fallujah could delay the already sputtering buildup to that offensive.

There has, however, been a growing push within the Iraqi military to recapture Fallujah first. Some of that pressure comes from Shiite militia forces besieging the city, which lies 40 miles west of Baghdad in Anbar province. The heavy presence of those Shiite militia fighters, who view much of the Sunni population as sympathetic to the Islamic State militants, has raised fears of sectarian reprisal killings during any operation, although military commanders said militias would stay at the city’s outskirts.

“We will tear down the black banners of the strangers who kidnapped the city,” Abadi said in his speech. “The clock of Fallujah liberation has rung, and the final victory is close.”

On Sunday, the Iraqi premier met with lawmakers and local officials from the province to inform them of military plans and efforts to protect civilians, his office said.

“Your sons, the heroic fighters in the armed forces, are preparing to achieve a new victory,” said Saad al-Hadithi, a spokesman for Abadi. “Liberating the city of Fallujah will be a victory for all Iraqis and will pave the way for the return of stability and normalcy to the province of Anbar.”

A recent wave of bombings in Baghdad has added weight to the calls of those who say that a Fallujah operation is more pressing than one for Mosul, with a militant hub so close to the capital putting civilians at risk. Meanwhile, Iraqi forces have scored a string of victories against Islamic State fighters in the province, most recently taking the desert smuggling town of Rutbah, with commanders saying they should build on successes there.

Sunni leaders from the province also have lobbied for an offensive, saying the continued siege of the city by military and militia forces is causing a humanitarian crisis inside; as many as 60,000 residents remain trapped without access to food and medical supplies.

“We call on all citizens who are still inside Fallujah to prepare to get out,” the military statement said, adding that secure routes would be organized later. Citizens who cannot get out should “raise a white flag” on their homes, it said.

But Jumaa al-Jumaili, a commander of local Sunni tribal forces, said the Islamic State is not allowing anyone to leave the city so that it can use residents as human shields.

“They desperately want to keep Fallujah because of its symbolic importance and location close to Baghdad,” he said. “But it’s almost besieged from all sides.”

He said that Shiite militia forces had agreed to fight on the outskirts of the city. “We want the people of Fallujah to rise against” the Islamic State, he said, adding that the presence of Shiite militia forces in the city would not help that aim.

Lt. Gen. Abdulwahab al-Saedi, who will be leading the operation for Iraq’s counterterrorism forces, said the army, police and Shiite militias will fight only on the outskirts of the city while his forces will “storm the center.” The operation will be “very, very soon,” he added, although he refused to give a timeline. He said that the U.S.-led coalition will give air support and that the battle will be “difficult but not impossible.”

“We do think they can do it,” said Col. Steve Warren, a Baghdad-based spokesman for the U.S. military, confirming that the coalition will provide air support.

Brig. Gen. Yahya Rasoul, the Iraqi military spokesman, also said the operation will begin “soon.” He described Fallujah as the “head of the snake.”

Police forces have arrived in recent days, with about 20,000 federal police officers with armored vehicles and artillery now on the city’s outskirts, said Lt. Gen. Raeed Shakir Jawdat, commander of the federal police.

Shiite militias have announced a buildup around the city. Saraya al-Jihad said it had sent units with rockets. Asaib Ahl al-Haq and the Badr Organization, two of Iraq’s most powerful militias, have called on civilians to leave.

The shift to regain Fallujah puts the buildup for a Mosul offensive in further question. Long-promised police forces that were intended to hold the ground and enable Iraqi forces to move forward have still not arrived.

Meanwhile, Maj. Gen. Najim al-Jabouri, head of the Mosul operation, has an openly fractious relationship with the Defense Ministry. He has complained that he has yet to receive a single tank on the front line for Mosul, where about 5,000 Iraqi troops have gathered and are struggling to hold on to a cluster of villages they managed to take from the Islamic State.

Said Warren: “We don’t expect this to impact the Mosul operation.”