Islamic State militants disguised in Iraqi army uniforms and driving stolen Humvees killed at least 40 Iraqi soldiers and captured 68 others in western Anbar province, breaking through a deteriorating Iraqi military offensive in an area where the United States recently broadened its airstrike campaign.

The wave of suicide bombings dealt a heavy blow to government efforts to rein in the militants, whose rampage has seized much of the country’s north and west — even as the U.S. and its allies began training Iraq’s Kurdish peshmerga fighters to bolster their ability to battle the Sunni extremists.

The attacks Sunday targeted troops stationed at Camp Saqlawiyah near the town of Sijir, 45 miles west of Baghdad. There has been no contact with the 68 captured Iraqi soldiers, who were though to have been taken to the nearby city of Fallujah, an Islamic State stronghold, said Gen. Rasheed Fleih. […]