WASHINGTON (AP) — Retired Marine Gen. John Allen will coordinate the broad international effort to battle the Islamic State militants, as the campaign against the extremist group ramps up and nations begin to determine what role each will play, U.S. officials said Thursday.

Allen, who has been serving as a security adviser to Secretary of State John Kerry, is expected to work with the nearly 40 nations around the world who have agreed to join the fight and help them coordinate what each will contribute, several officials told The Associated Press.