The Pentagon has announced it is expanding an “advise and assist mission” for U.S. troops in Iraq as some of them are deploying along with a conventional Iraqi army unit for the first time in years. In April, President Obama authorized U.S. combat advisers to deploy with Iraqi army forces at lower levels. Until then, they had been largely confined to bases and special forces missions. The announcement comes as officers have spoken about an “imminent” offensive against Mosul, the largest city held by ISIS. Earlier this month, the Pentagon raised the number of soldiers in Iraq to more than 4,600. There are also at least 3,000 U.S. military contractors in the country.