| UDHAIM DAM, Iraq
UDHAIM DAM, Iraq Wearing military fatigues and a white turban, the Shi'ite cleric gave an eve-of-battle address to Iran-backed fighters preparing to attack Islamic State militants in Tikrit, praising them for defending their faith and urging them to fight honorably.
Seated in front of him in rows, crossed-legged in the grass, were dozens of armed men from Iraq's largest Shi'ite militia, the Badr Organisation, the main element of a force now advancing on Tikrit's eastern flank against the Sunni Muslim Islamic State militants who now dominate most of northern Iraq.
This week's multi-pronged attack is the biggest coordinated assault on the city, best known as the home town of executed Sunni president Saddam Hussein, since the radical Islamic State fighters seized it in June.
It is also the clearest example of how Tehran, rather than Washington, is now playing a more important role on the battlefield in a war that sees both Iran and the United States supporting the same side against a common foe.
Unlike a rushed - and failed - Tikrit offensive in July, this campaign appears to follow the methodical military strategy honed by Iranian advisers in neighboring Syria, which helped President Bashar al-Assad regain some lost territory.
Iranian military commander Qassem Soleimani, along with two Iraqi Shi'ite paramilitary leaders, has overseen the eastern part of the Tikrit campaign, whose religious overtones are borne out in its operational title: 'Here I am, Messenger of God'.
Soleimani, a major general in Iran's Revolutionary Guards spotted on the battlefield here, is the commander of Tehran's elite Quds force, which Washington considers a banned terrorist organization responsible for training and arming Shi'ite militants across the Middle East.
At least 20,000 fighters are involved in the Iraqi advance, mostly from Shi'ite militias known as Hashid Shaabi (Popular Mobilisation) units. They are supported from the air by Iraqi jets, although not directly by a U.S.-led coalition which has targeted Islamic State positions elsewhere in Iraq and Syria.
Progress in the first three days of battle has been steady, often delayed by snipers and bombs on the road to Tikrit.
The advance has also been carefully prepared, from the armored bulldozers which dig berms to protect advancing forces every evening, to the sheikhs and "ideological guidance" units brought along to raise morale.
At Udhaim Dam, 75 km (45 miles) east of Tikrit, Sheikh Ahmed al-Rubaei, a Shi'ite cleric, repeated the government's message that the fighters should respect civilians in the predominantly Sunni Muslim city. Shi'ite militia have been accused of theft and atrocities after previous victories, a charge they deny.
"Let us not taint ourselves for something of no value. Today we are an ideological army," Rubaei told them. "I am not doubting you. You are honest, and above doing this. But I am reminding you just in case."
On the move, the attacking force is a confusing mass of armored vehicles, pickup trucks and motorbikes. The convoy, carrying hundreds of fighters, also includes jeep-laden artillery, ambulances, and armored police vehicles.
The Badr Organisation militiamen and the regular army's troops drive identical tanks, with only an army logo differentiating regular military from militia.
Above some of the army's armored vehicles, the banner of Shi'ite Islam's revered Imam Hussein flutters alongside the national Iraqi flag.
The forces start their day with dawn prayers. Then, if there are Islamic State fighters on the road ahead, artillery opens up to drive them back, targeting in particular suspected suicide car bombers. Armored vehicles advance to clear snipers, trying to avoid bombs planted by retreating militants.
The militiamen and soldiers say they have information about the territory ahead from military intelligence and sources in Islamic State territory. Sometimes that takes them on detours to bypass suspected booby-traps on their way.
Even so, the first two days of operation brought losses. Three blackened, bombed-out vehicles belonging to the army and militia forces could be seen on the road.
On Monday, crossing the hilly Hamrin region before descending into the flat Tigris plain, the fighters advanced only 8 km (5 miles). The next day, as Islamic State fighters evaporated, their progress was closer to 50 km.
As they advanced, they left police units and militia fighters to hold territory behind the frontline.
By mid-afternoon on both days, they set up base for the night. A bullet-pocked excavator, with metal armour-plating to protect the driver, dug a defensive wall for their base.
Driving alongside them in a white pick-up truck with loudspeakers and a Shi'ite banner on its roof, men from the Ideological Guidance unit dispense battlefield advice and blast out military songs to raise the fighters' spirits.
"Mosul is calling you," one of the songs - a favorite among the Badr Organisation - rings out, referring to the northern city which is the ultimate goal in Baghdad's military campaign to eliminate Islamic State.
The eastern force, which is targeting the town of al-Alam north of Tikrit, is one of three main axes of the campaign, the other two advancing along the Tigris river from north and south.
The militia fighters have already contacted the mainly Sunni al-Alam residents to say they will be well-treated if they put up white flags. But the campaign is clearly presented to the Shi'ite fighters as a defense of their sect, from Sunni radicals who consider Shi'ites heretics.
"Without you, the women of Karbala and Najaf will be enslaved," Rubaei told the fighters assembled in Udhaim before the fight, referring to holy cities that house the two most important Shi'ite shrines.
"Today, thanks to you, we are all victorious. Today we are in their hotbeds."
(Writing by Dominic Evans; Editing by Peter Graff)