With the worsening situation in Europe during the late 1930s, it behooved the British to prepare for war with its old enemy Germany. As such, many military programs were undertaken during this time some of which included attempts at strengthening the Army's armored corps. With this in mind, various light tank forms emerged through design and testing, some adopted and others not, and one product of this period was the diminutive Vickers "Tetrarch" Light Tank which went on to have a serviceable wartime career.
The design that ultimately became the Tetrarch began as a private venture initiative by the Vickers-Armstrong company. The company had made progress on an evolutionary line of light tanks and a new three-man design was set to continue some of the more proven qualities for a military market still seeking light-class armored combat vehicles. A pilot form from Metropolitan-Cammell Carriage and Wagon Company (a subsidiary of Vickers-Armstrong) was realized in 1937 to which testing then followed in 1938. At this point, the vehicle was known as the "PR Tank" and also recognized under the name of "Purdah".
Vickers engineers departed from earlier light tank design doctrine when finalizing the Purdah. Four large road wheels were set to each track side and the track link sections were thin in their width. The hull was rather basic looking and housed the driver at front-center. His position was behind a hinged armor panel with integrated vision slit offering basic protection - essentially an armor box was set over his head and shoulders to supply the proper amount of operating space. The turret housed the remaining two crew (commander and gunner) while lacking a cupola for the commander. He also doubled as the loader to the main gun. A smoke projecting system (found along the turret sides) could be used to shroud the tank's movements in combat. Armor reached between 4mm and 14mm which offered protection against small arms fire and shell splinters.
Running gear consisted of the eight aforementioned road wheels set with a track-and-wheel configuration. The engine was fitted at the rear of the hull and was made up of a Meadows 12-cylinder gasoline-fueled system offering road ranges out to 140 miles and road speeds up to 40 miles per hour. The chassis was suspended atop a coil spring suspension system for cross country travel support. The small tank utilized a unique steering system arrangement in which each road wheel was turned (in unison), twisting the track link sections, leading the tank in the desired direction.
Primary armament was a QF 2-pounder (40mm) main gun fitted to the turret. This gave the vehicle a decent weapon against light tanks of the period and a High-Explosive (HE) round could be used against dug-in enemy troops. 50 x 40mm projectiles were carried aboard and could be a mix of HE and AP (Armor-Piercing) rounds as needed. A "Littlejohn" adapter - a device used to increase the outgoing shell's velocity, affecting penetration value and range - was fitted to main guns of initial models. A 7.92mm BESA machine gun was fitted coaxially to the main gun for use as an anti-infantry measure. Some 2,025 x 7.92mm rounds of ammunition were typically carried for this weapon.
Before trials had ended, several changes were made to the basic design that included better engine cooling and improved travel ranges. These were met and the vehicle was placed into serial production. In September of 1939, the British declared war on Germany, placing the country on a course that could to be undone. In inventory, the tank was given the designation of "Light Tank, Mk VII (A17)". Aggressive German air raids on the factory delayed service entry until 1942.
Overall, some 177 Mk VII tanks would be produced by the end of 1942 (sources vary between 100 and 177). This was in time for first actions with British forces as they landed on Madagascar through Operation Ironclad. The "Battle of Madagascar" spanned from May 5th to November 6th, 1942 as British and Commonwealth forces faced off against Vichy French and Japanese enemies. The battle ended with an armistice on November 6th, 1942 and Free French authority established on the island.
Despite the seemingly useful compact fighting platform that the A17 was, the war quickly showcased the light tank category as a liability when major fighting powers began adopting medium-class tank systems. The 40mm main gun of the A17 became limited in combat, particularly against heavier armored foes. The vehicle was still useful for its speed and its anti-infantry prowess but little else, limiting it to reconnaissance or desperate infantry support actions as required. A stock of the tanks were shipped to the Soviet Army via Lend-Lease to help shore up losses on the East Front against Germany. A collection of Mk VII tanks was witnessed in action during the North African Campaign under the flag of the British 8th Army. During 1943, the Mk VII tank began carrying the nickname of "Tetrarch".
All hope was not lost on the role that the Mk VII tank was set to play in the war for 1941 saw the formation of the British airborne force at the behest of Winston Churchill. Churchill understood the value of airborne elements when witnessing their success through the German takeover of half of Europe using specialized surprise seize tactics from the air. This provided a second life for the small tank as a new glider was designed and developed for the purpose of carrying man, machine, and supplies into combat behind enemy lines - the General Aircraft Hamilcar.
The Hamilcar could fit a single A17 tank (or JEEP-type vehicle) in its hold while being towed by a transport aircraft. Once over the drop zone, the glider went free of its carrier aircraft and used its capabilities to land in an open field (preferably). The tank could then be prepared by its crew and driven off into combat where its speed and armament could shock unprepared, lightly armed foes.
Trials showcasing Hamilcars and vehicles were not conducted until 1944. Once a proven tactic, the Tetrarch was slightly revised for more of a close support role for infantry-minded takeover operations. This included fitting a 76.2mm howitzer in place of the 40mm tank gun which produced the designation of Tetrarch ICS ("Infantry Close Support"). The vehicle would follow ground operations and provide a hefty punch at range, aimed at dislodging enemy forces from their hiding places.
The Tetrarch's next notable service came during the June 6th, 1944 invasion of Northern France through D-Day - "Operation Overlord". The tank was featured in the follow-up wave of airborne drops which were used to secure positions being targeted by initial assault waves. About six Tetrarchs landed near the Orne River as part of the Airborne Armoured Reconnaissance Regiment where tanker crews made the most with what the nimble, yet highly vulnerable, light tanks could offer. At the very least they served as a strong defensive tool in the fighting - particularly for airborne forces that were typically ill-equipped and under-armed for prolonged engagements. The Tetrarch's final actions were during the Rhine River crossing of March 1945 through "Operation Varsity". By this time, however, the line had been given up almost exclusively for the American M22 "Locust" airborne-minded light tank.
There was work on several Tetrarch variants before the end of the war - one of which became the "Harry Hopkins" model - named after President Roosevelt's Lend-Lease administrator. This model saw its armor increase to 38mm thickness which sought to improve battlefield survivability. The modification also allowed engineers to rework some of the mechanicals of the vehicle based on combat service and at least 100 of the mark were built as "Light Tank, Mk VIII, Harry Hopkins (A25)".
Still another Tetrarch development entertained before war's end in 1945 was the Tetrarch "Alecto", another airborne-minded model intended for the support role. This mark fitted a 94mm howitzer for close support service but production ultimately yielded a limited batch. Other plans were in the works to fit even larger field guns to the chassis but not much came of this. A non-combat version, fitted with a dozer blade for engineering work, was seen before the end.
Tetrarch tanks remained in the British inventory into the years following World War 2. However, they were obsolete on the modern battlefield and given up for good by 1950 when the British airborne ended their support of the storied Hamilcar glider line. While initially of limited value when the war began, the Tetrarch came to its own rather interestingly by way of airborne forces and also served as Britain's first air-transportable tank.