British Army structure is broadly similar to that of the Royal Navy and Royal Air Force, with a single command (based in Andover, Hampshire) known as "Army Headquarters". Under the Army 2020 Command structure, the Chief of the General Staff is in charge of Army Headquarters. There are four lieutenant-general posts in Army headquarters: Deputy Chief of the General Staff, Commander Field Army, Commander Allied Rapid Reaction Corps and Commander Home Command. Army Headquarters is responsible for providing forces at operational readiness for employment by the Permanent Joint Headquarters. The command structure is hierarchical, with divisions and brigades controlling groups of units. Major units are regiment- or battalion-sized, and minor units are company-sized units (or platoons). All units are Regular (full-time) or Army Reserve (part-time). Naming conventions of units differ for historical reasons, creating some confusion; the term "battalion" in the infantry is synonymous with a cavalry, artillery or engineer regiment, and the infantry "company" is synonymous with an engineer or cavalry squadron and an artillery battery. The table below illustrates the different names for equivalent units.