The vanguard (also called the advance guard) is the leading part of an advancing military formation. It has a number of functions, including seeking out the enemy and securing ground in advance of the main force.
The vanguard derives from the traditional division of a medieval army into three battles or wards; the Van, the Main (or Middle), and Rear. The term Vanguard originates with the medieval French avant-garde, i.e. the ward in front. The vanguard would lead the line of march and would deploy first on the field of battle, either in front of the other wards or to the right if they stood in line.
The makeup of the vanguard of a fifteenth-century Burgundian army is a typical example. This consisted ofa contingent of foreriders, from whom a forward detachment of scouts was drawn
the main body of the vanguard, in which there traveled civil officials and trumpeters to carry messages and summon the surrender of towns and castles, and
a body of workmen under the direction of the Master of Artillery whose job it was to clear obstacles which would obstruct the baggage and artillery travelling with the main army.
In an English force of the period, the foreriders of the vanguard would be accompanied by the harbingers, whose job was to locate lodgings for the army for the following night.