– More than 25,000 Iraqi troops and militia fighters began a long-awaited operation Monday to retake the central Iraqi city of Tikrit, Saddam Hussein's hometown, from the Islamic State in Iraq and the Levant (ISIL) in what many see as a test of the central government's ability to retake and hold much of the territory lost to the terrorists last summer.

The operation was announced Monday by Iraqi state TV and came just one day after Iraqi Prime Minister Haider al-Abadi warned the restive Sunni tribes of central Iraq, many of which have sided with the proto-caliphate, that this was their last chance to rejoin the Iraqi central government.

Although the Iraqi army and its Iranian-trained and -equipped Shiite militia allies have attempted to capture Tikrit in the past, only to suffer embarrassing defeats at the hands of the well-equipped and disciplined ISIL fighters, Monday's operation appeared to be the most serious attempt yet, as tens of thousands of troops, militias and even a handful of local Sunni tribesmen encircled the city from four sides and began pushing into its center behind a heavy wave of artillery, rocket and airplane bombardment.

Capt. Ahmed Hilal al Jubouri, in a telephone interview from the main operations center in the nearby city of Samara, said that overnight the Iraqi air force had hit more than 30 ISIL targets after a day of artillery and rocket fire pounded the city from the south, the northwest and the northeast. He also said coalition aircraft had conducted a number of strikes. But at the Pentagon, spokesman Army Col. Steve Warren said the United States is not providing airstrikes because the Iraqi government did not request it.

'Thousand roadside bombs'

The main obstacle so far has been thousands of roadside bombs and booby-traps planted by ISIL in the approaches to the city, which Iraqi combat engineers have been dismantling at a furious rate, Jubouri said.

"All precautions have been taken for the success of the military operation and taking into account a thousand roadside bombs planted by [ISIL] on various buildings and on the roads, the engineering brigade effort initiated the process to dismantle those mines — more than 200 explosive device and more than 10 large car bombs were planted and ready to explode near the [Shiite militias] and security forces," he said.

Securing main highway

Taking Tikrit is seen as an essential first step in securing Iraq's strategic north-south highway, which links the capital, Baghdad, to Iraq's second largest city, Mosul, which has been controlled by ISIL since last June. Any operation to recapture Mosul — which will be a far bloodier and more complex undertaking than Tikrit — would require control over this highway before any major preparations could begin.

However, the high-profile role of the Iranian-backed militias might further exacerbate sectarian tensions in Iraq, where securing the cooperation of Iraq's large Sunni tribal population, which is openly suspicious of both the Shiite government and Iran, is considered essential to dealing with the ISIL threat over the long term.

One local resident, who refused to be identified out of fear of both ISIL and the Shiite security forces, said that in the past week at least a dozen top foreign ISIL leaders who had previously been publicly visible in preparing the town's defenses had left the city in advance of the assault.

Civilians flee, others slain

At least 5,000 civilians fled the city in the 72 hours proceeding the offensive, according to Capt. Jubouri, and many reported that other civilians who attempted to leave had been executed by ISIL in the streets as a warning to the civilian population to not the flee the town.

By nightfall Monday, the Iraqi security forces were reporting that they had pushed to within 3 miles of the city center, but this could not be independently confirmed. The Iraqi government has frequently exaggerated success on the ground during similar operations in the past.