WASHINGTON (AP) — As Iraqi tanks charge across the country to purge the city of Mosul of the Islamic State group, the United States has perhaps as much to gain from the operation as the Iraqis themselves. Wresting Iraq's second largest city from the extremists is key to eventually defeating them militarily, a major U.S. objective. Still, President Barack Obama's strategy to engage in this war without the use of combat forces has been received with some skepticism; some say this approach allowed IS to expand in the first place.