In addition to _Officers_, there are always connected with Head-Quarters a number of subordinates, such as interpreters, clerks, police, printers, lithographers, telegraphists, signallers, cyclists, motor-car drivers, orderlies, and postal employees, as well as grooms, servants, cooks, and drivers for the wagons which transport the offices and baggage of the Head-Quarters. Head-Quarters are therefore so large as to form virtually a Unit in themselves. This Unit requires a _Commandant_, or Officer responsible for its movement, quartering, and discipline, with perhaps a Quarter-Master-Sergeant to assist him. There would generally be with each Head-Quarters a small body of Military Police to maintain discipline, and Medical and Veterinary Officers to take charge of the health of the officers, men, and horses at Head-Quarters. The safety of Head-Quarters is so important that they must be provided also with Infantry to guard them, and Cavalry to form their escort when in rapid movement. VARIETIES OF STAFF The number and description of Staff Officers allotted to a Command depend on its importance, and on the duties they have to perform. The duty of the Staff Officer is defined as follows in British Field Service Regulations: “To assist the Commander in the supervision and control of the operations and requirements of the Troops, to transmit his Orders, and to assist the Troops in carrying them out.” In the British Service these duties are divided among three Branches of the Staff--the _General Staff_, the _Adjutant-General’s Branch_, and that of the _Quarter-Master-General_. The Staff has in foreign armies become differentiated into two Branches--the _Routine Staff_, which the Germans style _Adjutantur_; and the _General Staff_, which assists the Commander in all matters directly affecting the fighting. The Prussian General Staff is nearly a century old, and forms in general features a model of the General Staff more recently instituted in other armies. Its development from the Quarter-Master-General’s Staff is sketched in the historical part of this work. A short analysis of the main duties devolving on these different branches of the Staff will now be given. THE GENERAL STAFF The purpose of the Commander is to defeat his enemy, and in endeavouring to effect this object he has two main pre-occupations: 1. To watch the movements and forecast the plans of the enemy. 2. To make his own plans, and to decide on the movements and distribution of his forces required to carry them out. In order that the Commander may devote his whole attention to these vital matters, he should be as far as possible relieved from details, and these fall within the province of his General Staff. We thus see that the main duties of the General Staff should correspond to those laid down for the General, and may be summed up under the following heads: 1. _Intelligence_, to enable the Commander to watch the enemy’s movements, and make his plans.