WATCH: The Only Inside Look at the Islamic State

Vice News reporter spent three weeks with the extremist Sunni fighters, gaining an unprecedented glimpse into the inner-workings of the organization.

The aerial assistance given by the U.S. to Kurdish forces in northern Iraq has succeeded in halting the advance of the Islamic State (formely ISIS) on that front. On Monday, U.S. President Barack Obama said Kurdish and Iraqi forces took control of the strategic  Mosul Dam, which the Islamic State captured in previous weeks.

On Tuesday, Iraqi forces halted a short-lived offensive to recapture Tikrit, home town of executed dictator Saddam Hussein, due to fierce resistance from Islamic state fighters who have also threatened to attack Americans "in any place."

In Geneva, the United Nations refugee agency announced a major aid operation to get supplies to more than half a million people displaced by fighting in northern Iraq.

The Islamists' swift advance may have been halted – and reports claim some Sunni tribes in northwestern Iraq have begun to rise up against them – but the Islamic State still controls large swaths of territories in northwestern Iraq and across the border in Syria. The goal of an Islamic caliphate is still very much intact.

In rare feat of war correspondence, a reporter from Vice News accompanied Islamic State fighter for three weeks, documenting their rapid expansion since June. The video, originally aired in five parts, shines a light on the inner-workings of the organization, the enlisting of children, the treatment of minorities and more.