The President can appoint and commission, as a temporary second lieutenant of the Regular Army in time of peace, for the purpose of instruction and for a period not to exceed six months, any Reserve Officer who was appointed in the manner described in the two preceding paragraphs. A temporary second lieutenant will receive the allowance authorized by law for that grade and pay at the rate of $100 a month. He will be attached to a unit of the Regular Army for duty and training. At the end of the six months he will revert to the status of a Reserve Officer. DEPARTMENT COMMANDER'S REPORT At the end of each calendar year department commanders and chiefs of staff corps and departments compile lists of members of the Officers' Reserve Corps under their command, showing: (a) Name, rank, age, and address. (b) Amount of instruction received. (c) Progress made. (d) Efficiency of officer. (e) Recommendation. A copy of these lists will be forwarded to the Adjutant General of the Army. The remainder of this chapter boils down to an irreducible minimum some of the most important subjects with which a Reserve Officer or an applicant for a commission in the Officers' Reserve Corps should be familiar. It emphasizes those things with which a reserve officer should at once become familiar.[A] It merely opens up a broad field of study for a reserve officer and at the same time can be used as a place of reference. THE LAND FORCES OF THE UNITED STATES You now are, or expect to become, a member of the land forces of the United States. Of what do the land forces of the United States consist? They consist of the Regular Army, the Volunteer Army, the Officers' Reserve Corps, the Enlisted Reserve Corps, the National Army, the National Guard in the service of the United States and such other land forces as Congress may authorize. The land forces are grouped under two general heads: (1) The Mobile Army. (2) The Coast Artillery. "The Mobile Army. The mobile army is primarily organized for offensive operations against an enemy, and on this account requires the maximum degree of mobility." (Field Service Regulations.) It consists of: Infantry. Field Artillery. Cavalry. Engineers. Signal Corps Troops. "The Coast Artillery. The coast artillery is charged with the care and use of the fixed and movable elements of the land and coast fortifications." (Field Service Regulations.) The President of the United States is the Commander-in-Chief of the Army. He exercises his command through the Secretary of War. The Chief of Staff acts as military adviser to the Secretary of War. He puts into effect the Administration's wishes. For the purpose of equipping, inspecting, directing, and administering to the Army, there are the following corps and departments: