One of the recent trends in Roman military history has been an increased interest in the assessment of the ‘face of battle’. Adrian Goldsworthy's seminal work The Roman Army at War 100 BC–AD 200 followed John Keegan's approach in elucidating the probable realities of combat from the soldier's perspective. His work stimulated articles such as Sabin's ‘The Roman face of battle’ and Zhmodikov's ‘Roman Republican infantrymen in battle’. Other books also followed this trend, including Daly's Cannae and Kagan's Eye of Command. While all of these assessments have made significant contributions to the field, none of them have satisfactorily evaluated the specific dynamics of how commands may have been transmitted during a battle. This paper will assess vertical unit cohesion in the Roman army. This will include an analysis of the use of musical instruments and military standards in the process of transmitting battle commands. It will focus primarily on the tactical unit (i.e., the century) rather than the army as a whole. I will begin by evaluating our evidence for how trumpets may have been used in battle. Then I will review the evidence for the use of standards and their importance in troop positioning. Finally, I will bring this evidence together to put forth some possibilities regarding how standards and instruments functioned together in battle to command and control the tactical unit. The ramifications of this include our understanding of the details of combat technique, and the control of troop movement outside of pitched battle combat. All of this in turn gives us a greater overall understanding of the ‘face of battle’ and vertical unit cohesion in the Roman army.