The XO is typically responsible for the management of day-to-day activities, freeing the commander to concentrate on strategy and planning the unit's next move.
The decision by the Court was that the Federal Trade Commission was a quasi-legislative body because of other powers it had, and therefore, the president could not fire an FTC member for political reasons.
Congress can't retain removal power over officials with executive function (Bowsher v. Synar).
The standard is whether restriction "impedes the president's ability to perform his constitutional duty" (Morrison v. Olson, 487 U.S. 654 (1988)).
In most non-naval military services that are land-based (except the U.S. Army, where an executive officer is the second-in-command of certain units) or in joint military organizations, the executive officer is an administrative staff position versus a command position.
The term XO is not used in most British Army or Royal Marines units, where the designation second-in-command (2i/c) is used as a formal appointment.
However, the position does exist in some specialist regiments within the Royal Artillery where the exact duties vary.
In smaller vessels, such as submarines and frigates, the executive officer also holds the position of first lieutenant.
Originally, the second-in-command was usually referred to as the first lieutenant (or as "number one"), although it is becoming more common to hear the term XO.
The XO is typically responsible for the management of day-to-day activities, such as administration, maintenance, and logistics, freeing a commander to concentrate on tactical/operational planning and execution and a general officer commander to concentrate on similar planning and execution at the operational-strategic level.
While the experience gained as an XO is highly beneficial for an army officer's professional development, it is not necessarily a prerequisite for a command position.
The XO's own action station is in a separate part of the ship from that of the captain, so that a single hit will not likely incapacitate both officers.
This fleet up model was also adopted in the late 2000s for XO and CO positions of both large amphibious assault ships (but not aircraft carriers) and Arleigh Burke-class guided missile destroyers.
Like the Army, while experience gained as an XO is highly beneficial for an Air Force officer's professional development, it is not necessarily a prerequisite for a command position.
This position is typically held by a brigadier general or rear admiral (lower half) and is drawn from all of the armed services.
The duties involve serving as both an "executive assistant" to the SACEUR and also includes command responsibilities for the U.S. military community at Supreme Headquarters Allied Powers Europe (SHAPE) in Belgium.