The operation to drive the Islamic State, or ISIS, out of the key city of Mosul has begun, Iraqi Prime Minister Haider al-Abadi said in a televised statement Monday.
The fight for Mosul is expected to last for weeks, if not months.
The buildup to this assault has been in the works for some time, with the U.S.-led coalition and Iraqi forces hammering ISIS with airstrikes for more than a year.
According to CNN, the Nineveh Liberation Operations Center, which was set up to coordinate the operation, has brought in dozens of American and British advisers.
As for ISIS, many reports mention a growing network of tunnels that could help terrorists escape Mosul in the event of an attack.
The network of tunnels is said to stretch from the outskirts of Mosul to the nearby village of Hamdania, a source told CNN.
CNN reports that ISIS has allowed wounded fighters to leave Mosul and released low-level prisoners who were jailed for their beards, cigarettes or clothing.
In the days leading up to the offensive, fighting flared up outside the city, including an airstrike Sunday which badly damaged one of Mosul's main bridges, the al-Hurriya Bridge.
The al-Hurriya is one of five bridges connecting two parts of the city that are separated by the Tigris.
WATCH | Here's a look at the aftermath of the airstrike that targeted the bridge
ISIS militants locked both ends of the bridge to prevent people from using it after the airstrike.
Popular Mobilization Forces met with Iraq's prime minister Saturday to discuss the support of the Iraqi Security Forces during the imminent Mosul operations.
Masoud Barzani, the president of the Kurdistan Regional Government, tweeted Saturday, "The time has come to begin the liberation of Mosul."
In his statement, Barzani noted that Baghdad, the nation's capital city, and Irbil, the capital of Iraqi Kurdistan, agreed to establish a committee to supervise the happenings in Mosul after its liberation.
Mosul is the last major Iraqi city held by ISIS.