Although the M3 light tank was U.S. designed and built, it was the British who first took it into action during Operation Crusader which commenced on November 18, 1941 in northern Africa. In British service, the M3 was known as the Stuart and for Operation Crusader, 170 Stuart I light tanks were included in the order of battle for the British 8th. Army. As the battle unfolded, units equipped with the Stuart suffered significant casualties. This, despite the fact the Stuart compared very favorably against two of the most common Axis tanks, the Panzerkampfwagen III Ausf G and the Italian Fiat M13/40. Against the former, the two tanks were evenly matched in terms of speed and armor protection and both the Stuart's 37mm M6 gun and the PzKpfw III's 3.7cm KwK 36 gun could knock the other tank out from over 1,000 meters. Against the Fiat, the M3 dominated the Italian medium tank and the Stuart was invulnerable to the 47mm Cannone da 47/32 AT gun from 1,000 meters and beyond whereas the Stuart could penetrate the M13/40 almost anywhere at that range. Analysis following the Allied victory against Axis forces on December 30, 1941 showed that the high casualty rate had more to do with the skill of German tank crews and superior tactics. The British also found that the two-man turret of the Stuart was problematic, to the point that some Stuart crews tried to squeeze a third man in to facilitate gun handling. The Stuart also did not have a high fuel capacity in comparison to some British tanks (such as the Crusader) which limited its range to only 75 miles. Still, the British appreciated the mechanical reliability of the Stuart and excellent speed. Nevertheless, by mid-1942, the British relegated the Stuart to reconnaissance tasks only, avoiding tank-vs-tank combat wherever possible. The British continued to use the Stuart throughout World War Two. Subsequent models were the Stuart II (Guiberson diesel engined M3), Stuart III (M3A1), Stuart IV (Guiberson engined M3A1), Stuart V (M3A3), and the Stuart VI (M5 and M5A1).
The British also used a number of variants of the Stuart and two of the most common were the Stuart Recce and the Stuart Kangaroo. The Stuart Recce removed the turret which lowered the profile of the tank and lowered the weight of the vehicle which in turn, improved range. The Stuart Kangaroo also removed the turret and the vehicle was used as an armored personnel carrier (APC). There is debate on if the name “Kangaroo” was ever applied to the Stuart like it was to other similar vehicles derived from the M7 Priest, M4 Sherman, and Canadian Ram tank. These APCs were mostly used by British engineer units attached to armored brigades. A third, relatively common variant, was the Stuart Command which was also a turret-less Stuart but utilized by commanders and was equipped with additional radio equipment.
This, then, brings us to the subject of the photograph. It depicts a one-off modification to a Stuart in which a British Ordnance QF 18-pounder field gun, sans wheels, was fitted to a simple bracket mount in place of the tank's turret. Although many of these guns were converted into the improved QF 25-pounder gun prior to World War Two, a number of the older guns (which entered service in 1904) remained in service and saw action during the opening stages of the North African campaign. Whether this ad hoc self-propelled gun (or portée) was ever used in action remains unknown but it was certainly constructed during the North African campaign in 1941-42. An examination of the mounting suggests that the gun was centered on the upper hull with the box trail extending over the opening left by the removal of the turret. This would allow the gun to be elevated to a maximum of 37 degrees and permit recoil. Of course, this assumes the gun is the Mk. III or Mk. IV model. If, on the other hand, the gun was an older Mk. I or Mk. II with a single, central trail, then the maximum elevation was only 16 degrees. The gun crew would have operated the gun without the benefit of all-around protection with the only measure of defense coming from the gun shield. It appears that two of the three hull machine-guns (one front hull mounted and one in each side of the upper hull) were removed, likely to make room for ammunition. This left only the front hull machine-gun. If the intent was to provide mobility for the gun and its 6.3 mile range was its defense from enemy attack, then having the additional machine-guns wasn't needed and if need be, crew small arms could also be utilized for close-in defense. How much ammunition the modified Stuart could carry isn't known though with the shell being a little over 1 foot long, an adequate supply could likely have been stowed if the machine-guns and the ammunition for them was removed. How the crew entered the SPG is also not known. It may have been possible for the crew to slip underneath the trailing arm or perhaps the trailing arm was not secured to the rear deck and the gun could be tilted upward to permit the crew to enter. Certainly in action, three men would likely have been crewing the gun from the deck while another remained in the tank, passing ammunition up through the opening where the turret had been. Some have said the modified Stuart was used as an assault gun, utilizing the gun for infantry support in the direct fire role. However, this is unlikely given the high profile of the SPG, the lack of armor protection for the gun crew, and the relatively light armor of the tank itself.