The United States is stepping up its military campaign against Islamic State by sending hundreds more troops to assist Iraqi forces in an expected push on the city of Mosul, the militants' largest stronghold, later this year.
The additional troops, announced here on Monday by Defense Secretary Ashton B. Carter, are the latest escalation of the American military role in Iraq by Mr. Obama, who withdrew the last American soldiers from Iraq at the end of 2011. He began sending them back three years later after Islamic State fighters swept into the country from Syria.
Many of the newly deployed troops will be based at an airfield 40 miles south of Mosul that was reclaimed by Iraqi soldiers on Saturday.
Administration officials said the airfield would be critical to a successful military operation because the United States could use it as a staging area to provide logistical support to Iraqi forces as they try to retake Mosul.
The deployment will bring the official number of American service members in Iraq to 4,647. The United States had about 130,000 service members in the country about a decade ago.
The president said Iraqi forces had made important gains in the last several weeks. Most important, they retook Falluja, a victory that he said, “got a little bit lost in the news, but that’s a big town.”
The new deployment comes two years after Mr. Obama said that while the United States would help Iraq reclaim territory from the Islamic State, its efforts would “not involve American combat troops fighting on foreign soil.” Since then, he has steadily increased the number of troops and given them more authority.
Mosul is now the only major city in the country that the Iraqis do not control, and the Islamic State has not seized any substantial new territory since May 2015.
Source: The New York Times