It was in Mosul that Abu Bakr al-Baghdadi declared the establishment of Islamic State in Iraq and Syria (ISIS), a "caliphate" in the two Middle Eastern countries, and himself as leader of the extremist group.
The July 2014 appearance was his sole public appearance.
Mosul's population and urban size far exceeded that of Raqqa in Syria, the de facto capital of ISIS.
Mosul is well-equipped, both in agriculture and industry. The high oil production of Iraq's second-biggest city and its tax revenue once provided ISIS with an enormous source of income.
Located near the Syria-Turkey border, Mosul enjoys an exceptional geographical advantage.
Connected with the ISIS-controlled section in northern Syria, its expansive western deserts offered the extremists a wide range of space to operate throughout the two countries.
After two years of war, large stretches of Saladdin and Anbar provinces were successively recaptured by Iraqi forces. After the fight to retake Anbar's heartland Fallujah from ISIS, Iraqi forces spearheaded the next attack on Mosul - the extremists' last base in Iraq.
The city's eastern half was declared liberated on Jan 24, and after nearly a month of rest and reorganisation, the armed forces on Feb 19 announced a new operation on the western part of Mosul.
After four months of fierce battles, in early May, Iraqi forces entered the last stages of defeating the militants in western Mosul.
Iraqi forces launched their final push from multiple directions on June 18.
On June 21, ISIS bombed the city's landmark al-Nuri mosque as Iraqi forces were pushing closer.
On June 29, the capture of the mosque marked the end of the extremist group's stronghold in Iraq.