To a lesser extent, historical seniority is used to recognize status of honor given to early United States military leaders such as inaugural holders of certain ranks or those officers who served as leadership during major wars and armed conflicts.
The modern-day seniority system of the United States commissioned officer corps operates on two different levels.
For multi-national exercises, such as the Sharem event in South Korea, ships of foreign nations are sometimes given tactical seniority and thus may issue routine movement orders to United States vessels.
Actual combat would fall under the Task Force system, in which a United States admiral, with clear seniority, would take command over all vessels.
Groups of Army units, especially in active combat, may be placed under tactical command of any officer, regardless of rank seniority, for completion of a single mission.
By clear precedent, the holders of this rank (three persons in all) are senior to all other officers of the United States military, past and present.
Washington was referred to as "commander in chief" of the Continental Army, a title that since the adoption of the Constitution has been reserved for the (civilian) President.
The five star officers of World War II are technically considered the most senior officers in U.S. history (with the exception of the two "super ranks" previously mentioned), yet are often considered historically junior to the military leaders of the 19th century, especially the inaugural holders of senior military ranks.
Modern-day admirals and generals are typically not considered in lists of historical seniority, except for extreme cases such as leaders of wars or other wide scale armed conflicts.