The road from Baghdad to Tikrit is dotted with security checkpoints, many festooned with posters of Iran’s supreme leader and other Shiite figures. They stretch as far north as the village of Awja, the birthplace of Saddam Hussein, on the edge of Tikrit, within sight of the hulking palaces of the former ruler who ruthlessly crushed Shiite dissent.
More openly than ever before, Iran’s powerful influence in Iraq has been on display as the counteroffensive against Islamic State militants around Tikrit has unfolded in recent days. At every point, the Iranian-backed militias have taken the lead in the fight against the Islamic State here. Senior Iranian leaders have been openly helping direct the battle, and American officials say Iran’s Revolutionary Guards forces are taking part.
Iraqi officials, too, have been unapologetic about the role of the militias. They project confidence about their fighting abilities and declare that how to fight the war is Iraq’s decision, as militia leaders criticize American pressure to rely more on regular forces.
On Thursday, as they showed journalists around the outskirts of the battle, leaders of militias and regular forces alike declared that there was no distinction between the two; that the militias were a legitimate force under the government’s chain of command. And like the militiamen, many police officers and soldiers decorated their checkpoints and helmets with Shiite slogans and symbols.
What has been conspicuously absent in this fight, in the eyes of some Iraqis, has been the United States, whose airstrikes have assisted in earlier battles to roll back the Islamic State but have not been brought to bear in this new and crucial battle.
On Thursday, one of the militiamen, Mohammad al-Samarrai, 28, stood near a ruined mosque in the village of Muatassim, southeast of the city of Samarra, that he and his comrades had taken back from Islamic State militants on Monday. His face brightened at the sight of an American reporter, and he explained that he loved to see Americans because his brother had worked as an interpreter for American troops and now lives in Virginia.
But now, he said, he was confused that the United States did not seem to be throwing its full weight behind Iraq’s fight against the militants.
“After Saddam fell, American policy was helping the Iraqi people,” he said. “So why now are they helping the very same enemy that used to kill the American soldiers? If only they would remember the American soldiers killed by Al Qaeda.”
Kareem al-Jabri, a former teacher who now heads an artillery unit for the militias, known as popular mobilization committees, explained the new order of things more directly: “Iran is the principal supporter of Iraq, for the people and the army,” he said. “Iran is a real, true partner.”
Mohannad al-Ikabi, a spokesman for the militias, declared: “Iran is the only country that is actually responding to what is happening.”
But the commander of the Badr Organization, Mueen al-Kadhumi, joked that Americans had contributed to the fight — on the other side. He was referring to the Islamic State’s claims that an American suicide bomber had carried out an attack for the group on Monday. Near Muatassim, militiamen pointed to a crater that they said came from that explosion. A Badr flag has been planted beside the hole.
During the operation, Iraqi state television has sought to emphasize the competence and cooperation of militia and regular forces. While militias make up the bulk of ground forces, the Iraqi Air Force has carried out strikes, and Iraqi news channels have shown grainy pilot’s-eye footage of bombs hitting their targets — much like the ones often released by the Pentagon.
Thursday’s trip made apparent the complex nature of Iraq’s war effort. So far it has heavily relied on the Shiite militias, who are powerfully motivated by ISIS’s belief that Shiites are apostates who deserve death. But the militias’ involvement carries a risk of further inflaming sectarian tensions that ISIS has exploited — as has already happened in some places where Sunni residents have reported abuse or summary executions by the militias.
Officials said that as many as 5,000 local Sunnis had joined the counteroffensive for Tikrit. But Mr. Jabri, the artillery commander, and other militia leaders said their main function was not fighting, but providing intelligence and basic guidance to the militia fighters, who are mostly from Baghdad and southern Iraq and do not know the area.
Even as militia leaders declared that they were inseparable from the Iraqi state, the Shiite identity of the combined forces marching on Tikrit was on vivid display — jarring in an area long known as a Sunni stronghold.
The tour convoy began at the Badr Organization’s headquarters in Baghdad. There, over a breakfast of bread dipped in tahini, fighters embraced visiting clerics and recounted missions to Syria to defend the shrine of Sayeda Zeinab, holy to Shiites.
The fighters showed enthusiasm, expressed in both patriotic and religious terms. Many said they had left jobs to volunteer in the militia after Grand Ayatollah Ali al-Sistani, Iraq’s most senior Shiite cleric, called on all Iraqis to join the effort.
Vehicles were draped with the Badr flag and Shiite slogans. Religious battle songs blared from a sound system atop a bus; on its rear window, “God is Great” was spray-painted in pink.
The first stop along the road was Samarra, a mixed Sunni-Shiite city that was once a hub of Sunni insurgents fighting the Americans. Qaeda insurgents bombed a revered Shiite shrine there in 2006, provoking years of tit-for-tat sectarian attacks. Its dome, now half-rebuilt, glimmers gold beneath a scaffolding, and towering portraits of the Shiite imams Hussein and Ali now stand in a main traffic circle.
At federal police headquarters, there was a spread of grilled fish served beside Samarra’s reservoir, as the smoke of battle rose in the distance.
Many villages along the road seemed nearly empty, except for a few residents and shepherds who cautiously approached checkpoints on foot, holding white flags. The tour provided no time to talk to local Sunnis. But some said in separate interviews that they supported the effort and even the militias.
“They left their provinces to help us,” said Saleem al-Jabouri, 28, a government employee. “No one else has helped to liberate our areas, not even our tribal neighbors.”
At the edge of Tikrit, a blocked road marked the beginning of Islamic State territory. Militiamen worked a base that looked out on the city and Saddam’s palaces, once occupied by American soldiers, and more recently by ISIS.
At the base, Nizar al-Asadi, a militia member and engineer, compared the war effort to the battles of Imam Hussein 1400 years ago, adding, “His history is repeating itself.”
“Iraq is defending the whole world,” he said. “Your freedom is assured as long as you are with us.