Watch Part 2

Watch Part 3

A year after the Islamic State's lightning conquest of Iraq's second-largest city of Mosul, the poorly-trained and equipped Kurdish peshmerga forces are the international coalition's only reliable boots on the ground in northern Iraq.

The Pentagon's hopes of recapturing the city by spring 2015 have been dashed by the military failures of the Iraqi Army further south, leaving the peshmerga to defend a 600-mile long frontline almost encircling Mosul, fending off constant Islamic State assaults with insufficient supplies of ammunition and modern weapons.

In part one of a three-part series, VICE News embeds with Kurdish peshmerga fighters defending the hills above the Islamic State-held city of Sinjar.

Watch "A Year On From the Caliphate: The UK's Fight Against the Islamic State"

Read "The Islamic State is Here to Stay"