In a televised address, Prime Minister Haider al-Abadi pledged to raise the Iraqi flag over Mosul once more, calling on residents to cooperate with advancing forces.
The US-backed operation aims to push Isis (Islamic State) out of its de facto capital in Iraq. More than a million civilians are believed to be trapped in the city.
Dozens of ambulances were lined up at checkpoints on the edges of Iraq's northern region of Kurdistan, ready to ferry out casualties. Thousands of Iraqi troops have moved into position for the battle in recent weeks, and new military staging areas have sprung up along front lines.
The Mosul offensive marks a showdown in Isis' last major stronghold in Iraq. It was in Mosul's Great Mosque that Isis leader Abu Bakr al-Baghdadi announced his self-proclaimed caliphate more than two years ago.
"We will soon meet in Mosul to celebrate in liberation and your salvation," Abadi said, addressing the people of the city. "We will rebuild what has been destroyed by this criminal gang."But since then, the group's grip has slowly crumbled. Tikrit, Ramadi and Fallujah have been clawed back by Iraqi forces, with a heavy reliance on US-led airstrikes.
The battle for Mosul draws together tens of thousands of Iraqi troops from an array of the country's forces: Kurdish peshmerga soldiers, Sunni tribal fighters, army, police, Shia militias and elite counterterrorism units.
From the sky and on the ground comes close support from the US-led coalition. More than 80,000 troops are involved, including engineers and logistical support, said Major Salam Jassim, a commander with Iraq's elite special forces.
Despite sometimes competing agendas, the various armed forces have united, at least for now. At a staging area in a hamlet near Khazir, east of Mosul, Jassim and his men were waiting for the order for "zero hour". Battle plans were drawn out in black marker on walls and plastic tables. "We'll take it," Jassim said. "There's no doubt."
Troops have massed to the north, south and east of the city. Trucks packed with Iraqi soldiers and military vehicles have clogged the roads. Tanks, armoured vehicles and weaponry have been hauled nearly 400km from the capital, Baghdad.
For the first 48 hours, the offensive on the eastern front will be led by Kurdish peshmerga, Iraqi military officers said.
Brigadier General Haider Obaidi, another commander with Iraq's special forces, said: "We'll start after them and move after them to support them."
Police and Iraqi Army units will move up the main highway from Baghdad, while Shia militia forces are expected to focus on Tal Afar to the west and the town of Hawijah to the southeast. Kurdish peshmerga forces, Sunni fighters and the Iraqi army will also attack from the north.
Opinions are split on just how long and grinding the battle will be. Abadi has pledged to have the city back under Iraqi control by the end of the year. Jassim is not sure that's possible, with booby traps and explosive devices expected to slow the way. Civilians will complicate the battle. Between 1.2 million and 1.8 million are still inside the city, he said.
To avoid a humanitarian crisis, the Iraqi Government has asked civilians to stay in their homes, complicating air support and operations to clear neighbourhoods of militants. "The operation will take much longer because of this," Obaidi said. "For their safety, but it also means each neighbourhood needs to be surrounded and searched as we clear it."
Still, the US-led coalition will give closer support than in any other operation, he said, and Apache helicopters will probably be used. The coalition has requested that the airspace be cleared of Iraqi jets, whose air support will be limited to the areas where Shia militias are on the ground.
The western side of the city will be left largely open, which may make for a less protracted fight inside than if it was besieged. "We'll try to give them an escape to run to Syria," he said of the militants.
Brigadier General Yahya Rasoul, a spokesman for the Iraqi military, said that even if the western side is left open, it doesn't mean a safe escape for Isis. "If we do that, then this area will become a killing zone as we target them with our aircraft," he said.Iraqi forces have launched their most complex anti-Isis operation to date: retaking the country's second-largest city of Mosul. While the country's military has won a string of territorial victories that have pushed the Islamic State group out of more than half the territory the group once held, some Iraqi officials worry that the Mosul fight has been rushed and if the city is retaken without a plan to broker a peace, it could lead to more violence.
HOW WE GOT HERE
Mosul fell to the Islamic State group in June of 2014, when the extremist group blitzed across northern and western Iraq, overrunning nearly a third of the country and plunging Iraq into its most critical political and security crisis since the US-led invasion in 2003.
The most recent string of territorial victories for Iraqi ground forces have been in the country's west. Iraqi forces retook the city of Ramadi in late 2015, followed by a number of towns and villages along the Euphrates River valley and then Fallujah in June. This allowed Iraqi forces to weaken the group by cutting supply lines used to ferry fighters and supplies between territory held in Syria and Iraq.
Iraqi forces began moving into Nineveh province to surround Mosul in July, when ground troops led by the country's elite special forces retook Qayara air base south of the city. Thousands of Iraqi troops are now massing there ahead of the planned operation. Iraqi troops also deployed east of Mosul in the Khazer area, along with Kurdish Peshmerga forces, and to the north of the city near the Mosul Dam and Bashiqa areas.
In addition to the Iraqi army, Kurdish Peshmerga forces, Iraqi special forces and Sunni tribal fighters, Shiite militia forces are also expected to play a role in the Mosul operation. The role of the Shiite militias has been particularly sensitive, as Nineveh is a majority Sunni province and Shiite militia forces have been accused of carrying out abuses against civilians in other operations in majority Sunni parts of Iraq.
A very small number of Turkish troops deployed for over a year in Iraqi territory at a base north of Mosul have caused a recent spike in tensions between Iraq and Turkey. Iraq has repeatedly called for the Turkish forces to withdraw, claiming they entered the country without the permission of the central government. Shiite militia fighters have said they are violating Iraqi sovereignty and have vowed to expel them.
The fight to retake Mosul was largely launched from the north and east. The Kurdish peshmerga forces say they will push Isis out of a cluster of mostly Christian and Yazidi villages northeast of Mosul along the Nineveh plain, while Iraqi military troops try to cut the main supply line northwest of Mosul that links Isis territory in Iraq to its strongholds in Syria. A large number of Iraqi military forces are also expected to push up from Qayara air base.
Once villages around Mosul have been cleared of Isis fighters, Iraq's special forces " also called the counterterrorism forces " are expected to lead the push into the city of Mosul itself. The special forces were trained for more than a decade by the United States and are now some of Iraq's most competent ground forces. They have led the ground assault in a number of battles against IS in the past, including the operations to retake Tikrit, Ramadi, Fallujah and the Beiji oil refinery.
WHAT TO EXPECT
While Iraqi forces have won a number of territorial victories against IS over the past year, the Mosul fight is expected to be the most complex yet for the country's military. Mosul is Iraq's second-largest city and still home to more than a million civilians. Both in terms of geography and population, it's a much larger task than Iraq's military has ever undertaken previously in the fight against IS.
Iraq's military has been under enormous pressure to launch the operation to retake Mosul before the end of this year as Iraqi Prime Minister Haider al-Abadi has repeatedly promised Mosul would be retaken in 2016. Some Iraqi officials are concerned that the military operation is being rushed before the country's politicians have agreed on how the province will be governed after the Islamic State group is pushed out.
Iraq remains deeply divided, and the grievances between the country's Sunni, Shiite and Kurdish populations that allowed Isis to rise to power in the first place have not been resolved. Some Iraqi officials have cautioned that even after Mosul is retaken from Isis, violence will erupt again in the form of revenge killings or clashes between groups once allied against a common enemy.
Tuesday marks the second day of military operations by the Iraqi army, volunteer Shia and Sunni fighters as well as Kurdish Peshmerga forces to liberate the city of Mosul, the last stronghold of Daesh Takfiri terrorists in Iraq, which they overran in June 2014. Operations to free the city have been the subject of long planning, and the large-scale offensives are targeting the city from three different directions. Below is a series of live updates on the second day of the battle for Mosul.
— Iraqi fighter jets have targeted a convoy of Daesh terrorists as they were fleeing Mosul. A military source told Arabic-language al-Sumaria television network on Tuesday that the Iraqi military aircraft had struck 30 vehicles the previous night in an area close to the border with Syria. The source added that the slain terrorists, mostly non-Arabs, were escaping Mosul toward Raqqah, which is Daesh’s so-called headquarters in Syria.
— Hissam Abaar, a member of the Nineveh Provincial Council, has said that Kurdish Peshmerga forces are only 12 kilometers way from Mosul’s downtown and are making advances through Khazar region east of the city.
—Masoud Barzani, the president of Iraq’s Kurdistan Regional Government (KRG), has announced that up to 200 square kilometers were cleared in the first phase of the battle to liberate Mosul, thanks to close coordination between the Iraqi army and Peshmerga forces.