Combat Arms Is A Dirty Job!Ask any Soldiers with a Combat Arms Military Occupation Specialty (MOS) if they think their job is a dirty one and you will get a resounding YES! 11B Infantryman are the primary combat force for the US Army. Each Infantryman performs as a member of a fire team during ground combat operations. 13B Cannon Crewmember support Infantry and Tank units by providing indirect fire support (Artillery) using their Howitzer cannons. 11C Indirect Fire Infantryman