An extract on #troops
A cavalry soldier of private rank is called a trooper in many Commonwealth armies (abbreviated "Tpr", not to be confused with "trouper").
A related sense of the term "troops" refers to members of the military collectively, as in "the troops"; see Troop (disambiguation).
In some countries, like Italy, the company-level cavalry unit is called "Squadron".
Today, a troop is defined differently in different armed forces.
In the Australian Army a troop is the equivalent of a platoon sized element in units of certain corps, those being:
Royal Australian Armoured Corps
Royal Australian Engineers
Royal Australian Corps of Signals
Australian Army Aviation
Royal Australian Corps of Transport
Royal Australian Survey Corps (now disbanded)
Special Air Service Regiment (SASR)
The SASR is the only unit in the Royal Australian Infantry Corps to use the term troop to refer to its platoon size elements. SASR troops are also unusual as they are commanded by a captainmost troop/platoon sized elements are commanded by a lieutenant. In all cases, units which refer to platoon sized elements as troops refer to company-sized elements as squadrons and battalion-sized elements as regiments. Privates in the RAAC and SASR hold the rank "trooper", however this is not the case for any other Corps/units which use the term troops.
In the British Army the definition of a troop varies by corps.
Household Cavalry and Royal Armoured Corps: Three or four armoured fighting vehicles commanded by a subaltern, i.e. effectively the same level element as an infantry platoon. A unit of two to four guns or launchers, or an equivalent headquarters unit.
Royal Artillery: A half-battery. In the Royal Horse Artillery, a troop used to be the equivalent to a battery in other artillery units.
Royal Engineers, Royal Corps of Signals, Royal Logistic Corps, Special Air Service, and Honourable Artillery Company (and formerly the Royal Corps of Transport): A unit equivalent in size to a platoon in other corps, divided into sections or patrols. The Royal Engineers and Royal Corps of Signals used platoons instead until after World War II.
Other army corps do not use the term.
In the Royal Marines, a troop is the equivalent to an army platoon; a carryover from the organisation of the British Commandos in World War II.
In the Canadian Army, a troop is the equivalent of a platoon within the armoured, artillery, engineer, and signals branches. Two to four troops comprise the main elements of a squadron.
In the United States Army, in the cavalry branch, a troop is the equivalent unit to the infantry company, commanded by a captain and consisting of three or four platoons, and subordinate to a squadron (battalion). Companies were renamed troops in 1883.