The Initial Drill Evaluation tests each platoon’s ability to listen to the orders of its Drill Instructor at this point in training, and is a demonstration of the unit’s degree of discipline and esprit de corps. Drill is used as one of the first methods of transforming these recruits from civilians into Marines, and plays a large part on their development of teamwork and unit cohesion.
The object of close order drill is to teach Marines, through exercise, to obey orders immediately and in the correct manner. Close order drill is one foundation of discipline and esprit de corps. Additionally, it has long been, and remains, one of the finest methods for developing confidence and troop-leadership abilities in lower-ranking Marines.
Above information found on the Parris Island web site, September, 2009.