The U.S. 4th Infantry Division was originally tasked with entering northern Iraq through Turkey, however the Turkish government blocked the attempt.

Meanwhile, U.S. Special Forces and Peshmerga turned towards Mosul, securing the city on April 11 after the Iraqi Army V Corps surrendered.

[3] Towards the end of April, 20,000 soldiers from the U.S. 101st Airborne Division, led by Maj. Gen. David Petraeus arrived in Mosul and assumed responsibility for Ninawa province.

[5] Between 2004 and 2006, a stalemate existed between the Kurdish forces in the east of the city (who had been reflagged as the 2nd Iraqi Army Division) and Sunni insurgents who were firmly entrenched in western Mosul.

[5] In early 2007, coalition forces launched a new counter insurgency strategy throughout Iraq, mainly focused on Baghdad and the surrounding belts.

Mosul also had strong strategic importance as a main logistics hub for Al-Qaeda in Iraq because of its size and location - sitting at crossroads between Baghdad, Syria, Turkey and Iran.

The insurgents established a new base in Mosul and prepared for a 'decisive final battle' in the words of the Iraqi Prime Minister Nouri al-Maliki.

Two Iraqi Army battalions from the 2nd Division who had been deployed in Baghdad as part of Operation Imposing Law returned to Mosul.

[citation needed] On January 23, a massive cache of explosives was detonated in an abandoned building in Mosul in the Zinjeli neighborhood.

[citation needed] The troops, tanks and helicopters began arriving in Mosul on January 27, including elements of the 35th Brigade, 9th (Armored) Division.

On February 18, Coalition forces captured Abd-al-Rahman Ibrahim Jasim Tha'ir, Al Qaida's military emir for Mosul.

[13][14] On March 15, a force of between 10–12 insurgents attacked an Iraqi Army combat outpost with grenades, RPGs and small arms.

[15] On March 23, an insurgent suicide bomber, in a truck with a bullet-proof windshield, attacked Combat Outpost Inman, an Iraqi Army military base in western Mosul.

However, the Sunni Iraqi Accordance Front, said large numbers of gunmen had escaped to the Hamrin mountains following the start of the offensive.

The U.S. military spokesman, Maj. Gen. Kevin Bergner, announced that Iraq and U.S. forces had arrested 500 people and captured 5 weapons caches.

[25][26][27] On May 19, Iraqi forces reported that they had captured Abdul Khaleq al Sabaawi, the emir of Ninawa province, in a raid in Tikrit.

The same day in the town of Baaj, 130 kilometers from Mosul, gunmen ambushed a bus carrying police recruits killing 11 of them.

[28] On May 23, Iraqi police announced the capture of Abu Ahmed, an al-Qaida in Iraq financier for the three northern governorates of Salah-ad-din, Kirkuk, and Ninawa.

On June 2, a suicide bomber with a car packed full of explosives targeted the Ninawa police station in eastern Mosul, killing 13 people, including five policemen, and wounding 50 others.

[31] On June 4, insurgents ambushed a U.S. military patrol in the town of Hawija, in the neighboring Kirkuk Governorate, killing three soldiers.

[33] On June 26, a car bomb attack targeted the offices of Ninawa Provincial Governor Duraid Kashmula in Mosul.

He had been a close associate of Abu Musab al-Zarqawi, the most notorious leader of Al-Qaeda in Iraq, who was killed in an airstrike two years before.

A terrorist force that once numbered more than 12,000, with AQI strongholds in the west and central regions of Iraq, has over two years been reduced to a mere 1,200 fighters, backed against the wall in the northern city of Mosul.