The United States is quietly rushing dozens of Hellfire missiles and low-tech surveillance drones to Iraq to help government forces combat an explosion of violence by a Qaeda-backed insurgency that is gaining territory in both western Iraq and neighboring Syria.

The move follows an appeal for help in battling the extremist group by the Iraqi prime minister, Nuri Kamal al-Maliki, who met with President Obama in Washington last month.

But some military experts question whether the patchwork response will be sufficient to reverse the sharp downturn in security that already led to the deaths of more than 8,000 Iraqis this year, 952 of them Iraqi security force members, according to the United Nations, the highest level of violence since 2008. […]