At the First Battle of Manassas, 21 July 1861, it became cruelly apparent that the Army of the Potomac did not possess the field medical support assets and doctrine to deal with the wounded in action (WIA) resulting from such large and destructive armies. Thus, under the direction of Surgeon Jonathan Letterman, Medical Director of the Army of the Potomac, dedicated medical evacuation vehicles and trained litter bearers were established along with very strict rules of operation. At the same time, Dr. Letterman established a more efficient and better quality field hospital. Even with a vastly improved field medical support system established in the Army of the Potomac, the medical evacuation above division level and field hospital support in total were inadequate during and after the Gettysburg Campaign. This was due to several significant factors, but three were of primary importance: first, General Meade's decision to allow dr. Letterman to bring up only a portion of the Army of the Potomac's field medical support system; secondly, the lack of organized medical services between the division and base or general hospitals, which left the care of the wounded at Gettysburg in disarray when Dr. Letterman moved most of the field medical support south with General Meade immediately after the Gettysburg Campaign; and the large number of casualties.