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Mark VI tank
Mark VI tank
from Wikipedia

Wooden mockup of the proposed Mark VI, 1917

The Mark VI was a British heavy tank project from the First World War.

Design

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After having made plans for the continued development of the Mark I into the Mark IV, the Tank Supply Committee (the institute planning and controlling British tank production) in December 1916 ordered the design of two new types of tank: the Mark V and the Mark VI. The Mark V had to embody the most advanced features that could still be incorporated into the Mark I hull. The Mark VI should abandon the old hull entirely, reflecting only some general principles of the older tank.[1]

On 13 July 1917, Metropolitan, the firm associated to Sir William Tritton, had a wooden mock-up ready of both models.[2] As no design drawings of the Mark VI have survived, the pictures made on that date (and earlier on 23 June 1917 of the still partly unfinished models) form the major source of information.

The Mark V design still looked a lot like the Mark I. It had many changes in detail however, including smaller sponsons with cylindrical machine gun mounts, a lengthened hull, a larger cabin and a machine gun position at the back.[3] This design was ultimately abandoned due to enormous delays in the development of the Mark IV. The tank eventually taken in production under that name was not the Mark IV, as originally planned, but basically a slightly changed Mark I. When at last in December 1917 the desired new engine and transmission could be built in, it was this type which became known as the Mark V.

The Mark VI design had a completely different hull, which was higher with rounded tracks on the front.[1] It had no real sponsons; the side doors replacing them having protruding machine gun positions. The main armament was a single 57 mm gun low in the front of the hull. The driver is sitting in a square superstructure much further back, the corners of which each had a machine gun. On the superstructure a raised lookout post for the commander was fitted.[1] It is known from a surviving text that the hull was to be compartmentalised with a separate engine room on one side containing also in line the drive gears of both tracks, the drive shaft for the track of the opposite side crossing the hull. Wider tracks (75 cm) were to be used. It was to be protected by fourteen millimetres of armour.[1]

Cancellation of production

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When in September 1917 US headquarters in France decided to create a separate American Tank Corps with 25 battalions, among which five were to be Heavy Tank Battalions, Major James A. Drain ordered 600 of the most advanced British tank, being at the time the Mark VI.[4] However, this endangered the plans of Albert Gerald Stern, then coordinating allied tank production, to produce a common Anglo-American tank, the Mark VIII. In December 1917 he ordered to halt the project. Not even a prototype was built.

References

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from Grokipedia
The Mark VI tank was a British project developed during as an advanced iteration of the preceding Mark V, incorporating a front-mounted 6-pounder gun, six Hotchkiss machine guns, wider tracks for improved mobility, and a more compact design to facilitate , though it progressed no further than a wooden mock-up prototype. Conceived in the aftermath of the 1917 Battle of , the Mark VI addressed frontline feedback on earlier British tanks by eliminating the bulky side sponsons that housed armament, repositioning the 150 hp engine to the side for better , and raising the commander's cabin for enhanced —features that influenced later designs like the Mark VIII. An initial order for 600 units was placed for the , but production was canceled in favor of the Anglo-American Mark VIII due to the high costs of retooling factories and shifting priorities amid the war's end. With specifications including a weight of 27 tons, dimensions of 8.05 meters in length, 2.53 meters in width, and 2.64 meters in height, the was projected to achieve a top speed of 7.4 km/h and a range of 72 km on its 8-16 mm armored hull, crewed by eight personnel. Its armament combined the 57 mm QF 6-pounder gun for anti- and support with the six 7.71 mm machine guns, blending elements of the "male" and "female" variants from prior Marks into a more versatile configuration. Despite its innovative traits, such as the ability to cross 10-foot trenches and a focus on lighter loading for faster deployment, the Mark VI remained a conceptual rather than a battlefield asset, underscoring the rapid evolution of technology during the conflict.

Development and Production

Historical Context

The development of British tanks during began with the Mark I in 1916, introduced as a response to the stalemate of , featuring a rhomboidal hull design to cross obstacles and sponsons for mounting armament on the sides. Subsequent models, such as the Mark II and III, served primarily as training vehicles but incorporated minor refinements, while the Mark IV, entering service in 1917, added thicker armor and relocated fuel tanks for better protection against fire. These early designs faced significant challenges, including sponson-mounted guns that increased the vehicle's width to over 13 feet, complicating and battlefield maneuverability, as well as multi-crew operations requiring up to eight men in a single undivided compartment shared with the engine, leading to coordination difficulties, heat, fumes, and fatigue. The in 1916 marked the tanks' combat debut at Flers-Courcelette, where 49 Mark I tanks were deployed, but mechanical unreliability caused most to break down or become mired in mud before reaching objectives, underscoring the need for more robust engines and tracks. Similarly, the in 1917 exposed limitations during advances over shell-torn terrain, with tanks like the Mark II struggling to keep pace with , prompting demands for faster and more maneuverable vehicles to exploit breakthroughs effectively. These engagements highlighted the heavy tanks' sluggish speed—typically under 4 mph—and vulnerability to terrain, driving requirements for designs that could achieve greater cross-country mobility without sacrificing armor. In December 1916, the Tank Supply Committee, evolving from the earlier Landships Committee, ordered the parallel development of the Mark V and Mark VI to address these shortcomings, with the Mark V focusing on incremental upgrades to the existing hull and the Mark VI envisioning a more radical redesign for enhanced performance. The United States' entry into the war in April 1917 further influenced this trajectory through Anglo-American cooperation, as American observers studied British designs and the U.S. Tank Board recommended adopting the Mark VI for its heavy tank battalions, leading to initial orders for hundreds of units to bolster Allied production capacity. This collaboration later transitioned to the joint Mark VIII project, a larger heavy tank intended for mass production by both nations.

Design Initiation and Prototyping

The development of the Mark VI tank began in December 1916 when the Tank Supply Committee, chaired by Major Albert Gerald Stern, placed an order for both the Mark V and Mark VI models as part of an effort to advance British armored vehicle designs. The design was led by Director of Engineering Walter Wilson. This initiative followed the successful deployment of earlier Mark series tanks and aimed to incorporate a redesigned hull that eliminated the bulky side sponsons of previous models, allowing for more streamlined transport and potentially enhanced tactical flexibility. The committee, established shortly after initial tank trials, sought to accelerate production to meet the escalating demands of the Western Front. In early 1917, prototyping efforts focused on constructing a full-scale wooden mock-up to validate the proposed changes. The Metropolitan Carriage and Wagon Company, a key contractor involved in earlier production, conducted demonstrations of the full-scale wooden mock-up on 23 June and 13 July 1917 at their Birmingham works, with the mock-up having been completed prior to the initial demonstration. This mock-up featured the new hull configuration without sponsons and served as the primary physical representation of the project, allowing engineers to assess structural feasibility before committing to . The drew brief influence from ongoing Mark V improvements, such as enhanced mechanical reliability, to inform the Mark VI's layout. The project's international dimension emerged in September 1917 when the , preparing to form its own tank corps upon entering the war, placed an order for 600 Mark VI tanks under the direction of Major James A. Drain, the U.S. representative on the Anglo-American Tank Commission. Drain, appointed as American Commissioner in December 1917, prioritized the Mark VI as the most advanced British heavy tank available, intending it to equip American heavy tank units for deployment in . This order reflected growing Allied coordination but was ultimately affected by shifting production priorities. No original design drawings for the Mark VI have survived, necessitating reliance on contemporary photographs of the mock-up, committee minutes, and postwar historical reconstructions to understand its configuration. These records, preserved in archives such as the , provide the basis for modern analyses of the tank's intended form. Early evaluations of the wooden mock-up emphasized concepts for improved speed and single-driver control, addressing limitations observed in prior Marks where multiple crew members were needed for steering. Committee discussions in April 1917 highlighted a target speed increase through lighter construction and a engine integration, while the single-driver system aimed to simplify operations by centralizing control mechanisms. These assessments, conducted during the mock-up's demonstration, confirmed the viability of the redesign but remained conceptual due to the project's limited progression.

Cancellation and Aftermath

In December 1917, Albert Gerald Stern, chairman of the Tank Supply Committee, ordered the cancellation of the Mark VI tank project to prioritize resources for the Mark VIII "International" tank, a joint Anglo-American design intended as the new standard Allied . This decision came amid broader pressures from tank shortages, where production capacity was stretched thin across multiple designs. The cancellation stemmed from significant resource reallocation challenges, as factories already geared for Mark VI components would require extensive retooling to accommodate proposed changes, rendering further production prohibitively time- and cost-intensive. No metal prototypes or production units were ever constructed, leaving the project to conclude with only a single full-scale wooden mock-up completed in mid-1917. The , which had placed an order for 600 Mark VI tanks in September 1917 to equip its nascent tank corps, promptly withdrew the contract following the cancellation, redirecting efforts toward joint production of the Mark VIII instead. This shift ensured that British and American manufacturing lines focused on the more advanced international design, avoiding duplication in wartime output. Despite its abrupt end, the Mark VI exerted some post-cancellation influence on subsequent British tank programs, particularly through the partial adoption of its raised cabin concept in the Mark VIII's final configuration, which improved crew visibility and command efficiency.

Technical Design

Hull and Armor Configuration

The Mark VI tank introduced a redesigned hull that departed significantly from earlier British heavy tanks, featuring a higher profile with rounded front tracks to improve visibility and obstacle clearance. This configuration eliminated the prominent side sponsons used in prior marks, allowing for a narrower overall width and better maneuverability, while side doors provided access points and positions for machine gun mounts. The armor consisted of riveted steel plates with a frontal thickness of 14 mm, tapering to 10 mm on the sides and rear, and 6 mm on the roof and bottom, offering protection primarily against small arms fire and artillery shrapnel but vulnerable to field guns. Internally, the hull was compartmentalized for enhanced safety and efficiency, with a separate engine compartment isolated from the central crew areas to minimize noise, heat, and fire hazards, and dedicated storage for ammunition positioned away from the fighting compartment. The design accommodated a crew of eight in the raised central section. Key dimensions included a length of 8.05 m, width of 2.53 m (supported by 75 cm-wide tracks), and height of 2.64 m, resulting in an approximate weight of 27 tons—lighter than the Mark V's 29 tons due to the streamlined structure without sponsons.

Armament and Defensive Features

The Mark VI tank was designed with a primary armament consisting of a single QF 6-pounder (57 mm) gun, featuring a short 64.7 cm barrel, mounted low in the front hull for support. This configuration represented a significant from earlier British heavy tanks, centralizing the main gun in the hull rather than distributing similar weapons across bulky side sponsons, thereby streamlining the vehicle's profile and enhancing tactical flexibility. Complementing the main gun, the Mark VI incorporated six 0.303-inch (7.7 mm) Hotchkiss air-cooled machine guns for secondary armament and close-defense roles. These were positioned to provide comprehensive coverage: four in ball swivel mounts integrated into the raised front and rear (two forward and two aft), and two additional guns in compact side sponsons. This arrangement allowed for 360-degree fire without requiring crew members to expose themselves, a defensive improvement over prior marks that relied on larger, more vulnerable sponson-mounted weapons. The machine guns were supplied with a total of 10,000 rounds of ammunition, distributed across belts to sustain prolonged engagements. Defensive features emphasized crew protection through the strategic placement of these machine gun positions, which were embedded in the superstructure and side elements to enable suppressive fire against infantry and light threats from all angles. By eliminating the cumbersome full-length sponsons of predecessors like the Mark V—which had housed dual 6-pounder guns—the Mark VI achieved a lower silhouette and better mobility while maintaining robust all-around defensive capabilities via the protruding ball mounts and reduced sponson design.

Engine, Transmission, and Mobility

The Mark VI tank was equipped with a straight-six , a water-cooled unit producing 150 horsepower at 1,250 rpm, positioned in a separate compartment on the side of the hull to improve and minimize crew exposure to exhaust fumes compared to earlier designs where the engine was centrally located. This relocation allowed for a more balanced layout, contributing to the tank's overall lighter weight of approximately 27 tons. The transmission featured a Wilson epicyclic gearbox, an advancement that enabled operation by a single driver, eliminating the need for multiple crew members to handle steering as in previous marks like the Mark IV. This system integrated gearing and differential functions, providing smoother control and four forward speeds with reverse, which was a significant step toward simplifying tank operation. Mobility was enhanced through several design choices, including tracks widened to 75 cm to reduce ground pressure and improve performance over soft terrain. The tank achieved a top road speed of 4.6 mph (7.4 km/h) and an operational range of 45 miles (72 km), suitable for support but limited by the era's technology. The suspension remained rigid, similar to prior marks, relying on the rhomboidal track frame with cranked axles for obstacle clearance, but was optimized for the lighter hull to provide better stability without added complexity. capacity was approximately 200 imperial gallons, allowing for sustained operations without frequent refueling.

Specifications and Comparisons

Key Specifications

The key specifications of the proposed Mark VI tank, derived from historical design records and mock-up data since no prototypes were constructed, are presented below for reference.
CategorySpecification
Weight27 tons
DimensionsLength: 8.05 m; Width: 2.53 m; Height: 2.64 m
Crew8
Armor8–16 mm
Armament1 × 57 mm gun; 6 × 7.62 mm (0.303 in) machine guns
Powertrain150 hp
PerformanceMaximum speed: 7.4 km/h; Range: 72 km
These values represent estimated parameters based on the intended design goals, including a target speed of approximately 7.4 km/h to match operational requirements of contemporary heavy tanks.

Comparison to Contemporary Tanks

The Mark VI tank represented an evolutionary step in British heavy tank design during World War I, introducing innovations aimed at addressing the limitations of earlier models like the Mark V. Unlike the Mark V, which had a crew of eight including a single driver to operate its dual 57 mm guns mounted in side sponsons, the Mark VI proposed a single-driver control system with a centralized 57 mm gun positioned low in the front hull, eliminating sponsons entirely for enhanced maneuverability and a narrower profile (2.53 m wide compared to the Mark V's approximately 4.1 m with sponsons extended). This design allowed for better ventilation and reduced crew exposure during reloading, while maintaining similar top speeds of around 4-5 mph and armor thickness of 8-16 mm, but the Mark V's established production (over 400 units) and proven reliability in combat ensured its deployment, whereas the Mark VI remained a prototype. In contrast to the Anglo-American Mark VIII (also known as the Liberty tank), the Mark VI's raised crew cabin directly influenced the later model's design, providing improved visibility, though the Mark VIII retained sponsons for its armament while incorporating all-around defense through multiple machine guns. However, the Mark VIII featured thicker armor (up to 16 mm) and a more powerful 300 hp Liberty engine, enabling a higher top speed of about 5.3 mph (8.5 km/h) and better cross-country performance over the Mark VI's 150 hp engine and 4.6 mph limit, at the cost of greater weight (37 tons versus 27 tons). The Mark VIII's emphasis on joint production and superior power output ultimately led to its prioritization, sidelining the Mark VI amid resource constraints. Compared to the French , the British Mark VI embodied the contrasting doctrinal approaches of the Allies: the FT's compact 6.5-ton frame, 39 hp , and top speed of about 5 mph prioritized rapid support and with its rotating turret mounting a 37 mm gun or and armor up to 22 mm, whereas the heavier Mark VI (27 tons) focused on breakthrough roles with superior firepower from its 57 mm gun but sacrificed agility due to its slower, less nimble configuration. This highlighted the British preference for robust, -accompanying heavies over the French emphasis on lighter, more versatile designs that influenced evolution. Overall, the Mark VI sought to bridge the gap between heavy infantry support tanks and improved mobility, offering potential advantages in crew efficiency and compactness over predecessors like the Mark V, yet its cancellation in favor of inter-Allied projects like the Mark VIII—driven by production timelines and strategic shifts toward the war's end—prevented these benefits from materializing in combat.
FeatureMark VIMark VMark VIII
Weight (tons)2728-29376.5
Top Speed (mph)4.655.35
Armor (max mm)16161622
Main Armament1 × 57 mm2 × 57 mm (male)2 × 57 mm1 × 37 mm
Engine Power (hp)15015030039
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