While Iran insists that it has no combat units in Iraq, just trainers and advisors, mainly for pro-Iranian Shia militias, there are a lot of Iranian weapons showing there, usually not far from the Iranian border. American UAVs regularly patrol the border area and the Americans and Iranians have an unofficial agreement not to shoot down each other’s UAVs. The UAVs regularly note Iranian military vehicles entering Iraq. The Americans also have photo satellites regularly passing overhead that see this as well. Thus the Americans know that there have been several hundred Iranian M-60s and T-72 tanks and other armored vehicles operating with the Shia militias inside Iraq. There have also been a lot of Iranian truck mounted rocket launchers. The tanks and rocket launchers often have Iraqi crews largely because older Iraqi Shia who were conscripted to serve in the army as tank or artillery crews when Saddam ran the country. The Iranian rockets tend to be based on Russian designs and thus are familiar to Shia veterans of the Iraqi army.
The Iraqis also know how to improvise and often mount smaller rocket launchers on the backs of civilian trucks or pickups. Another frequently seen combat vehicle inside Iraq is the Iranian Safir. This is an Iranian made 2.3 ton vehicle that is almost identical to the American World War II vintage jeep (which the U.S. stopped using in the 1980s). The Safirs often have a machine-gun or rocket launcher mounted in the back and the Shia militiamen were trained to use dozens of these in an attack, moving forward in a “swarm” while firing and, at least for the ill-trained ISIL gunmen, overwhelming defenders.