The position of Supervisor is a very critical one in the Technocratic Fronts, even as it is merely another position equal in status to no small few battlefield combatants. Wheras other units are dedicated towards actually clearing the battlefield and safeguarding civilians, the job of a Supervisor is to oversee conditions over the field of battle and relay orders down the chains of command to units on the field. By gathering and consulting various overlays and video scans of the battlefield to determine positions of friendly, enemy, and neutral forces, and sending out messages through subordinates, radio, and animal messengers to coordinate movements and attacks, the Supervisor ensures that forces of the Combine are where they need to be, and that threats can be realized and dealt with before they overwhelm Technocratic armies. Three key facets are considered when promoting a person to the position of Supervisor - merit, charisma, and distance.
Merit is a part of many if not all positions in the Combine, actually, but plays a particular importance for Supervisors. Experience in dealing with large numbers of people, as well as effective communication and the transmission of orders and requests in one of if not THE biggest thing a Supervisor needs to have, and they can come from most any field of work as long as they've managed to gain this merit in some form. In practice, many Supervisors originate from the very military chain of command they are a key part of: While a civilian originated Supervisor may be talented and skilled, soldiers tend to regard those from military backgrounds as more trustworthy or understanding of the way things work, and so tend to exert bias whenever an opportunity comes up.
Charisma is a part of merit, to be sure, but can stand on its own as well. A Supervisor who is ineffective at winning the hearts of their superiors, subordinates, and counterparts faces little success in the future, for they will not be listened to, or asked to deal with the most sensitive (and therefore recompensensed) matters. Charisma comes in many forms, from those who manage to establish a web of connections and contacts on and off the battlefield to those that can bark commands and be obeyed out of sheer stature.
Finally, distance. Even though a Supervisor needs to know how to lead and to connect, they are still ordering men and women, and sometimes even their coworkers, into areas where they may very well die. A Supervisor needs to be able to connect to his or her fellows, yes, but also to recognize the potential of death and learn to prevent their emotional dams from bursting when those people die until they can come to a point where it will not affect their performance.
Much like their coworkers in other fields, Supervisors in fact have an entire entire sub-army of people and machines to directly serve and assist underneath them. Rarely seen if at all on the battlefield, these people instead relay the commands of the Supervisor to appropriate field elements, keep track on the state of the battlefield, ensure proper supply and dispersal of equipment and troops, and ensure overall that everything keeps running as smoothly as possible in the bases and organizational committees so that the frontliners may do their jobs effectively, and vice versa. Much like their coworkers, a Supervisor is a powerful and incredible asset to keeping organization and calm - but, again much like their coworkers, without the multitudes of people and units to assist them, the Supervisor would never be able to handle all that is required to keep control over the battlefield.