The desert towns of Al-Qaim and Rawa near Syria's border in the Euphrates Valley, where Iraqi forces launched operations Thursday, constitute the final Islamic State group bastion in the country.
The US-led coalition battling the jihadists has called the assault "the last big fight" and capturing the region will help drive a final nail into the coffin of the IS experiment in cross-border statehood.
- Long-time jihadist bastion -
Long before the rise of IS, Al-Qaim became renowned as a hotbed of jihadist insurgency in the wake of the US-led invasion in 2003.
The strategic and porous border became a magnet for foreign fighters entering Iraq from Syria, which Baghdad accused of turning a blind eye, and a key smuggling route for arms and illicit goods.
Coalition troops carried out repeated operations with codenames like Matador and Steel Curtain in 2005 to flush out Al-Qaeda jihadists.
The roughly 150,000 people living in the Al-Qaim region -- with 50,000 inside the town itself -- are Sunni Muslims from a small number of influential tribes.
The town lies at the heart of a wealthy agricultural region and was once a railhead for the phosphate mining centre of Akhashat in the desert to the south.
In the era of president Saddam Hussein before the invasion, Al-Qaim's huge chemical factory treated uranium to feed Iraq's nuclear programme.
But American air strikes in 1991 and then United Nations inspections transformed the factory into a metallic skeleton.
- IS takeover -
IS fighters seized control of Al-Qaim in June 2014 as the group captured vast swathes of territory in a lightning rampage across Iraq.
Under IS, the town has been a vital supply route between its forces in Iraq and the oil-rich city of Deir Ezzor it once controlled over the border in Syria.
The area has reportedly served as an important hideout for senior IS leadership and was struck repeatedly by coalition air strikes.
An Iraqi general estimates there are over 1,500 IS fighters left around Al-Qaim.
- Forces facing IS -
The Iraqi forces now closing in on Al-Qaim comprise crack government troops hardened by months of gruelling fighting against IS and irregular fighters from the Hashed al-Shaabi coalition under Baghdad's command.
Crucially. Sunni tribal volunteers in the Hashed have been heavily engaged alongside the Iran-trained Shiite militias that dominate the umbrella group.
The Sunni fighters come mainly from the major local tribes, providing a key element in an area some 500 kilometres (300 miles) northwest of Baghdad where tribal law often trumps central authority.
The fighting in the barren region, using artillery and sand berms, will differ drastically from the ferocious urban combat that Iraqi forces encountered as they seized back the biggest IS-held city of Mosul.
While Iraqi forces are squeezing IS on their side of the border, the jihadists are battling competing offensives, also in the Euphrates Valley, over the frontier in Syria.
© 2017 AFP