Since 2014, we talked a lot about a terrorist group named ISIS. That stands for Islamic State in Iraq and Syria. And that's what ISIS wants to create based on its severe interpretation of Islamic law. The group is infamous for mass murdering people who don't share its beliefs.
In June of 2014, ISIS took control of Mosul, the second largest city in Iraq.
Today, it's ISIS' most significant stronghold outside of Syria. And Iraqi troops and militia are getting ready to try to take it back. U.S. troops are also involved. There are several thousand of them currently in Iraq, and with a major battle looming in the months ahead, smoke fills the sky.
SUBTITLE: ISIS' battle tactics.
ARWA DAMON, CNN SENIOR INTERNATIONAL CORRESPONDENT: This is the Qayyarah power station, more about 65 kilometers to the south of Mosul, with the Iraqi army. That cloud of black smoke you see there, that is actually a fairly common ISIS tactic to try to impair the visibility of coalition aircraft and drones. But it is particularly effective in this area because what they're burning around here, that is crude oil.
There are oil fields that according to the commander, ISIS used to move around 100 tankers of crude a day. That is up until the Iraqi security forces moved into this particular area.
Now, to the north and east of Mosul, you have the Kurdish Peshmerga positions. They have had a defensive berm in that area for around the last two years. But in recent weeks, they have moved forward from the southeast towards Mosul, as well as capturing some key villages. And in doing that, they have come across some now fairly common ISIS tactics as well underground tunnels. The Iraqis themselves have uncovered homemade ISIS weapons, mortar tubes and mortar themselves, larger than anything the Iraqi say they have at their disposal.
According to the commander of the Nineveh operations, he says that as they moved closer to Mosul, ISIS is using less foreign fighters, more local fighters and they're not putting up as strong of a resistance, saying that they're seeing them flee quite more frequently. Is this because ISIS is running out of fighters, or is it because they are trying to build up their resources to defend Mosul? That commanders are unclear about, but they do believe that they will be able to fulfill the prime minister's goal of liberating Iraq's second largest city by the end of the year.
Of course, the crucial question at this stage is, even though there is a plan to assault the city, is that plan going to mean winning the fight?