The U.S. support mission for the battle of Mosul is not likely to require additional troops beyond the 600 just authorized by President Barack Obama, a military spokesman in Baghdad said Thursday.
The military can't guarantee how the offensive will develop, "but I can tell you we believe we have all the forces we need to help the Iraqis liberate Mosul," Air Force Col. John Dorrian, spokesman for Combined Joint Task Force-Operation Inherent Resolve, said in a video briefing to the Pentagon.
Defense Secretary Ashton Carter announced Wednesday that 600 more troops would be sent to Iraq to provide logistics and maintenance support, as well as the training and enabling function, for the Iraqi Security Forces now massing at the Qayyarah West airfield about 40 miles southeast of Mosul.
The 600 service members will bring the total number of U.S. troops in Iraq to slightly more than 5,000.
In his briefing, Dorrian said the U.S. is stepping up air and artillery strikes in the "shaping operations" to prepare for the attack on Mosul, a city of two million before the forces of the Islamic State of Iraq and Syria, or ISIS, swept into Iraq in 2014 against little resistance by the Iraqi army.
He said that U.S. and coalition airstrikes in the last 30 days have killed 18 ISIS leaders -- 13 of them in Mosul. "By taking these individuals off the battlefield, it creates some really disruptive effects to enemy command and control" for the coming battle, Dorrian said.
The airstrikes have largely stopped the group from attempting to bring in reinforcements by convoy, but some fighters are still able to trickle into Mosul individually or in small groups, he said.
ISIS is estimated to have 3,000 to 4,500 fighters in Mosul, Dorrian said.
Iraqi Security Forces will have eight to 12 brigades, or up to 30,000 troops, for the offensive, plus Kurdish Peshmerga forces arrayed to the east, north and west of the city, Dorrian said. The offensive is expected to come up the Tigris River Valley from the south.
A major concern for the U.S. is how the Iraqis will handle what is expected to be a massive flow of Mosul residents -- known as internally displaced persons -- fleeing the city once the attack begins.
In the retaking of Fallujah in Anbar province earlier this year, human rights groups and the United Nations charged that Shia Popular Mobilization Units, allied with Iraqi Security Forces, committed atrocities in the "vetting" of refugees to weed out ISIS fighters.
Dorrian said as many as 800,000 displaced persons might come out of Mosul, and the U.S. is working with Iraqi Prime Minister Haider al-Abadi to ensure their safety. Abadi "has been very clear about that," Dorrian said.
Abadi has also cautioned the Kurds against seeking to expand their territory beyond the generally recognized Kurdish autonomous region in the fighting for Mosul.
Abadi said after a meeting in Baghdad on Thursday with Kurdish leader Masoud Barzani, "The aim of the battle should not be territorial conflicts but to free the citizens from the persecution" of ISIS.
-- Richard Sisk can be reached at Richard.Sisk@Military.com.