The 4/73 (Sphinx) Special Observation Post Battery Royal Artillery frequently deploys surveillance and target acquisition patrols, which often operate far from the primary force, behind enemy lines. They deploy fire support teams to brigade reconnaissance forces or other reconnaissance elements to aid in calling in accurate artillery strikes.

The unit was established in 1982 predominantly in response to the rising tensions brought on by the Cold War. If the Soviet Union were to launch an offensive into Western Europe, small squads from 4/73 would create covert hide sites along expected invasion routes. Once overrun by Soviet forces they would call in intelligence reports and artillery strikes on rear segments of the invading force.

The unit performs comparable missions to 148 Battery. One of the significant distinctions is 4/73 lacks the parachute and commando training required of 148 members. 4/73 consists of four patrol troops and a battery headquarters. Three of the patrol troops form a three-man HQ element and two six-man patrols. A smaller patrol troop with an HQ element and just one six-man team stands ready to support 16 Air Assault Brigade.


4/73 has been deployed in recent times to Afghanistan and Iraq. During operations in Afghanistan the unit changed from its regular artillery spotting role to a reconnaissance role. Patrolling in Land Rover Defender XD WMIKs (Weapons Mount Installation Kit) around Afghanistan, the soldiers of 4/73 provided vital intel while supporting infantry units in the area with fire support teams. In April 2007, 4/73 served as part of 12 Brigade (Brigade Reconnaissance Force, or BRF) for Operation Herrick VI. That operation then became Herrick VII in October, at which point 4/73 contributed troops to 52 Brigade’s BRF, serving alongside a recce detachment from the Yorkshire Regiment, 2nd Battalion.