While Iraqi troops advanced further into territory held by the so called “Islamic State” in their campaign to recapture Mosul, they found a mass grave which holds about 100 bodies, many of them decapitated. AP footage shows bones and decomposed bodies dug out of the ground by a bulldozer. This Iraqi federal police officer holds a stuffed animal he found on the site.

The grave, found near the town of Hammam al-Alil near Mosul, proves to be a dark testimony to the „Islamic State’s“ brutality. IS militants have carried out a series of massacres since seizing large areas of southern and central Iraq in 2014. This photo shows a member of the Iraqi security forces inspecting a building that was used as a prison by Islamic State militants in Hammam al-Alil.

These displaced Iraqi men from the Hammam al-Alil area celebrate their liberation as they return to their homes after the recapture of their village by Iraqi forces from Islamic State.

Oil wells have been set ablaze by IS in an apparent response to the ongoing military offensive to drive the extremist group out of its stronghold. A military commander said more than 5,000 civilians have been evacuated from eastern parts of Mosul and taken to camps. The surprise attack showed that even while under siege, the group could still sow chaos in parts of Iraq far from its base in Mosul.

Smoke rises during clashes between Peshmerga forces and IS militants in the town of Bashiqa, east of Mosul. Initially used by the "IS" to establish their caliphate and henceforth the key source of prestige and resources, Mosul is also the base for IS’s chemical weapon operation. The ancient Assyrian city also has formed a vital source of tax revenue and forced labor.

Iraqi special forces take cover as their unit comes under fire from an Islamic State sniper. Together with Kurdish Peshmerga and Shiite militias, Iraqi forces intensified fighting and moved into more densely populated areas of the city without air support from the US-led coalition due to the high-risk of civilian casualties.

Meanwhile, Kurdish peshmerga forces decided to focus on other strongholds of resistance in northern Iraq and on the Kurdish-controlled city of Kirkuk, where IS initiated a campaign of violence in response to the advances of the Iraqi army towards Mosul.

The United Nations says over 34,000 people have been displaced from Mosul since the operation began on October 17, with about three quarters settled in camps and the rest in host communities.

The "Islamic State" (IS) — also known as ISIL, ISIS and Daesh — is an al-Qaida splinter group with a militant Sunni Islamist ideology. It emerged in the aftermath of the US-led invasion of Iraq in 2003 and is led by Abu Bakr al-Baghdadi. Their goal is to create a worldwide "caliphate." It gained worldwide notoriety in 2014 after a blitzkrieg military campaign that resulted in the capture of Mosul.

IS is believed to be operational in more than a dozen countries across the world. It controls territories in Iraq and Syria. However, the group has lost much of the territory it controlled in Iraq and Syria at the height of its expansion in 2014.

The US leads an international coalition of more than 50 countries, including several Arab nations. Russia, Iran and its Lebanese Shiite ally Hezbollah, which all support the Syrian government, also fight IS. Regional forces such as the Kurdish peshmerga (above) and US-backed Syrian Kurdish fighters, fight IS on the ground. The Iraqi army and militia have pushed IS from large parts of the country.

One of IS' main sources of income has been oil and gas. At one point, it controlled an estimated one-third of Syria's oil production. However, US-led airstrikes deliberately targeted oil resources and the Syrian government as well as US-backed Syrian Kurdish fighters have retaken most oil wells. Other means of income include taxes, ransom, selling looted antiquities and extortion.

IS has claimed responsibility for numerous terrorist attacks across the globe. The militant group has targeted capitals across the EU, including Berlin, Brussels and Paris. IS leaders have encouraged so-called "lone wolf" attacks, whereby individuals who support IS carry out terrorist acts without the direct involvement of the group.

The group uses various tactics to expand its power. IS fighters have looted and destroyed historical artifacts in Syria and Iraq in an attempt at "cultural cleansing." The group has also enslaved thousands of women from religious minority groups, including Yazidis. IS also uses a sophisticated social network to distribute propaganda and recruit sympathizers.

IS has further exacerbated the ongoing Syrian conflict. Millions of Syrians and Iraqis have fled their homes, many traveling to Europe in pursuit of refuge. Although it has lost all of its strongholds, the militant group has left extraordinary destruction in its wake. Areas affected by the militant group's rule will likely take years to rebuild.