The convoys were the first clear sign of a new player on the battlefield in the U.S.-backed offensive to retake Mosul from Islamic State: Hashid Shaabi or Popular Mobilization Forces (PMF), a coalition of Shi'ite militias.
Although it reports officially to Prime Minister Haider al-Abadi, the coalition is mostly made up of groups trained by Iran and loyal to its Supreme Leader, Ayatollah Ali Khamenei.
They have close ties with General Qassem Soleimani, the commander of Iran's Quds Brigade, the extra-territorial arm of Iran's Revolutionary Guards. He was seen touring the frontlines around Mosul last week.