A quartermaster general is the staff officer in charge of supplies for a whole army.
In the Imperial German Army, while a Quartiermeister was a non-commissioned officer in charge of supplies, a Generalquartiermeister did not deal with supplies, but with operational command. He was the most senior officer below an Army's Chief of Staff.
For example, during the First World War, Erich Ludendorff was Generalquartiermeister to the German Second Army in August 1914. With his expert knowledge of the plans for the assault on Liege, which he had helped to draw up, he was sent to supervise that assault and took personal charge when the brigade commander was killed.
More famously, when Paul von Hindenburg was appointed Chief of the General Staff at the Oberste Heeresleitung (OHL or "Supreme Army Command") in August 1916, Ludendorff, who had been his Chief of Staff in the East, came with him. Ludendorff declined to be known as "Second Chief of the General Staff" and instead chose the title First Quartermaster-General - in which role he directed the operations of the German Armies and wielded power over German politics and industry.
The Quartermaster General of the United States Army is a general officer who is responsible for the Quartermaster Corps, the Quartermaster branch of the U.S. Army. The Quartermaster General does not command Quartermaster units, but is primarily focused on training, doctrine and professional development of Quartermaster soldiers. The Quartermaster General also serves as the Commanding General, U.S. Army Quartermaster Center and School, Fort Lee, Virginia and the traditional Quartermaster Corps. The office of the Quartermaster General was established by resolution of the Continental Congress on 16 June 1775, but the position was not filled until 14 August 1775. Perhaps the most famous Quartermaster General was Nathanael Greene, who was the third Quartermaster General, serving from March 1778 to August 1780. The first Quartermaster General to serve in the U.S. Army was Thomas Mifflin of Pennsylvania.
The position of Quartermaster General originated in the Continental Army, under order of Congress. On 16 June 1775, 2 days after the birth of the Army, Congress ordered the creation of both a Quartermaster General and a Deputy Quartermaster General. During this period Quartermaster Generals would be act like chiefs of staff for the commanders of the Continental Army, acting as the prime supplier and businessmen for dealing with civilians, operated and repaired supply lines, which included the roads which they traveled upon, was responsible for transporting troops and furnished all the supplies needed to establish camps when the troops got there.