Kurdish fighters, backed by US-led air strikes, have captured several villages in an attempt to retake the Iraqi town of Sinjar from Islamic State (Isis) militants who overran it more than a year ago. Thousands of Yazidis living in Sinjar were killed and enslaved by IS, causing the flight of tens of thousands of people. This focused international attention on the Islamist group's violent campaign to impose its radical ideology, and prompted the US to launch air strikes against the militants.

The major objective of the offensive launched on 12 November is to completely cut off Highway 47, which passes Sinjar and indirectly links the militants' two biggest strongholds — Raqqa in Syria and Mosul in northern Iraq — as a route for goods, weapons and fighters. Coalition-backed Kurdish fighters on both sides of the border are now working to retake parts of that corridor.

US-led coalition air strikes pounded IS-held areas in the town, as around 7,500 Kurdish special forces, peshmerga and Yazidi fighters descended from the mountain that shares its name with the town towards the frontline in a military convoy. However, Sinjar is not an easy target. One attempt by the Kurds to retake it stalled in December. The militants have been reinforcing their ranks in Sinjar recently in expectation of an assault. "On the radio we hear [IS] calling for reinforcements from Syria," Rebwar Gharib, a deputy sergeant on the central front line in Sinjar, said.

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Kurdish fighters, backed by US-led strikes, try to retake Sinjar from Islamic StateSafin Hamed/AFP
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Kurdish forces take part in an operation backed by US-led strikes in the northern Iraqi town of SinjarSafin Hamed/AFP
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An Iraqi Kurdish fighter take part in an operation to retake SinjarSafin Hamed/AFP
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Smoke rises from the site of US-led air strikes in the town of SinjarAri Jalal/Reuters
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Heavy smoke covers the northern Iraqi town of SinjarSafin Hamed/AFP
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A member of the Kurdish Peshmerga forces use a mirror to scan his surroundings during clashes with Islamic State militantsAri Jalal/Reuters
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A female Kurdistan Workers Party (PKK) fighter stands outside a base in SinjarAsmaa Waguih/Reuters

The Kurdistan Workers' Party (PKK) has trained a Yazidi militia in Sinjar, while tribal groups operate independently. Several thousand Yazidis have also joined the peshmerga. For Yazidi forces taking part, the battle is very much about retribution.

IS inflicted a wave of terror against the minority Yazidi community, members of an ancient religion whom the Islamists view as heretics, accusing them of worshipping the devil. An untold number were killed in the August 2014 assault, and hundreds of men and women were kidnapped – the women enslaved and given to militants across the group's territory in Iraq and Syria, many of the men believed killed, others forced to convert.

Tens of thousands of Yazidis fled into the mountains, where the militants surrounded them, leaving them trapped and exposed in the blazing heat. The crisis prompted the US to launch air drops of aid to the stranded, and then on 8 August 2014, it launched the first round of air strikes in what would mark the beginning of a broader coalition effort to battle the militant group in Iraq and Syria.

Some of those stranded on Mount Sinjar were rescued by Syrian Kurdish fighters, who cleared a path for the Yazidis to descend from the mountain, cross into Syria, then cross back into northern Iraq's Kurdish autonomous zone. Then in December, Kurdish fighters in north-western Iraq managed to drive the militants out of areas on the other side of the mountain, opening a corridor that helped many of the remaining displaced Sinjaris to escape. Those Kurdish fighters then tried to advance into Sinjar town itself but were fought off by the IS militants.

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Yazidis displaced by IS play volleyball in Zakho, northern IraqJohn Moore/Getty Images
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Shengal Sarhan, 1, is cared for by his siblings at their temporary home in Zakho, northern IraqJohn Moore/Getty Images
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Mahmood Kheder Hassan, 75, and his wife Khefshe Hamad, 68, who were displaced by IS attacks, stand near their temporary home in Zakho, northern IraqJohn Moore/Getty Images
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A Yazidi man lights oil lamps in the temple of Lalish, the holiest site of the Yazidi religion, in Lalish, Nineveh Province, IraqJohn Moore/Getty Images
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Sheikh Mirza, 84, prays at the entrance to the temple of LalishJohn Moore/Getty Images
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A Yazidi boy kisses a figure of a black snake at the entrance of the Temple of LalishJohn Moore/Getty Images
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A Yazidi priestess baptises a baby with springwater at the Lalish templeJohn Moore/Getty Images
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Yazidi boys line up to pray at their religion's most holy temple in Lalish, IraqJohn Moore/Getty Images
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Women sweep the temple of Lalish, the holiest site of the Yazidi religionJohn Moore/Getty Images
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Workers sweep the courtyard of the Temple of Lalish, the most holy site of the Yazidi religionJohn Moore/Getty Images
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Yazidi boys ride past an oil refinery after leaving the temple of LalishJohn Moore/Getty Images

Most Yazidis have been displaced to camps in the Kurdistan region; several thousand remain in Islamic State captivity.