U.S. defense officials have bristled under criticism from Iraqi officials and others that the campaign against Islamic State is stalled or moving too slowly. U.S. Central Command is eager to show that airstrikes are having an effect on the ground and that the American and Iraqi militaries have a plan to continue to drive fighters out of their key strongholds in Iraq.

U.S. officials said they don’t have a good estimate of the current size of Islamic State forces, although they were once estimated at up to 14,000. They concede that Islamic State fighters still control large parts of northern and western Iraq, but say much of the Kurdish-controlled areas have been reclaimed. Islamic State captured Mosul, a city of 600,000, in June at the start of its blitz across parts of Iraq…

A coalition of Iraq’s most experienced military forces, including Kurdish fighters known as Peshmerga and U.S.-trained Sunni fighters, would be ready by the spring or early summer to begin the offensive to retake Mosul, said Gen. Austin, the chief architect of the international military campaign against Islamic State fighters in Iraq and Syria.