A Corps of Drums is a musical unit of several national armies. Drummers were originally established in European armies to act as signallers. This is the major historical distinction between a military band and a corps of drums, 'drummers' would not play their instruments to entertain or delight, but rather as a utilitarian battlefield role. This role was fulfilled by trumpeters or buglers and timpanists in the cavalry and the artillery, who did not form into comparative formed bodies in the way that drummers did; therefore, an orthodox corps of drums will exist in the infantry arm and not in other arms (save for the light infantry).
Most fife and drum traditions trace back to the Swiss mercenaries of the early Renaissance, and it is known that by the early 16th century, each company of infantry soldiers would have a single drummer and a single fife player. These two musicians would march at the head of the company, and when not providing uplifting marching tunes, they would be used by the company commander to convey orders, on and off the field of battle. The drummers would be more aptly described as signallers than musicians, as shouted orders were very hard to hear over the din of battle. Later, a bugle would become the preferred means of communication on the battlefield, and the drummers adapted, training on bugles and carrying them in battle, but retaining the drum and the title of drummer.
As time went on, the individual drummers and fife players in each company would be organized at battalion level. They retained their role in each company in battle, but would form one body of men at the head of a battalion on the march. It was necessary to appoint a Drum Major (the equivalent of a Sergeant Major, for the drummers) to be in charge of the drummers and to organize training in the emerging discipline of military drumming while a fife major was to be appointed to be the principal fifer and to train future fife players. The corps of drums would group together when not on duty with each company, and carry out various roles within the battalion, such as administering military justice and ensuring soldier's billets were secured, thus, the corps of drums became attached to the battalion HQ and was organized at battalion level, as opposed to individual company level.
Eventually, as the use of musical instrument on the battlefield diminished, corps of drums looked to fill specialist roles within the battalion while still retaining their original role for ceremonial purposes.
Several different strings of logic have seen corps of drums employed in many varied roles. Because the corps would often be employed in support of the battalion, in areas such as delivering mail or designating billets, they are often given the role of assault pioneers, or supporting-fire (machine gun) platoons. The corps of drums role on the battlefield was originally to signal orders, and therefore some units are organised into signals platoons, operating radios. Corps of drums were also deployed to march under the parley flag when officers of opposing met to discuss terms of surrender, etc. Therefore some corps of drums perform a liaison role.