IBRAHIM BIN ALI, Iraq — The predominantly Sunni agricultural area east of al-Karma is dotted with dusty date palms rising amid slow-moving waterways, trenches and buildings used as temporary bases or abandoned in various states of destruction. The fight against the Islamic State (IS) will likely prove tougher in this province, Anbar, than any other in the Iraq.

The government-allied, primarily Shiite militias known as the Popular Mobilization Units played a key role in retaking sections of Anbar, but were reportedly withdrawn from around Ramadi, the provincial capital, beginning April 10 in response to a US demand. They, however, remain in positions in other areas of the province.

In the battle for Tikrit, the militias’ ground forces early on and US airstrikes later in the fighting proved crucial to the victory over IS there. Following reports of abuses by the militias in some liberated towns and local Sunni tribes’ opposition to the use of Shiite militias in the area, the United States is said to have refused to continue airstrikes near Ramadi unless the militias were withdrawn from the fighting.

On the front line near the IS-held town of al-Karma earlier this month, Al-Monitor watched as fighters from the Badr Organization — flying the militia's flag higher than that of the national Iraqi forces' on a protective earthen embankment — fired at IS positions. Sniper fire from the other side ensued.