World War 1 taught all of the world's armies that tanks would soon be replacing the mounted cavalryman. Such an evolution would, in turn, require all-new tactics in combat. During the war, some mechanical tractors were in use to help with resupply of frontline troops but the trusted and true wheeled wagon was still the major form of resupply transportation - even into the post-war period. The arrival of the tank and its fast-moving tactics made the need for reliable mobile supply and support quite clear to warplanners. Artillery and caissons drawn by horses simply could not keep up with the mobile mechanized army of the day for tanks and accompanying infantry needed artillery support to be ready at a moment's notice. During World War 2, the Germans understood this need quite well and developed the "15cm Schweres Infanteriegeschutz 33/3 auf Selbstfahrlafette 38(t) (Sf) Ausf. M" - marked in the German Army inventory as the "SdKfz 138/1" and better known as the "Grille" (or "Cricket"). Now, artillery could range in front or in-between advancing allied tanks and support infantry maneuvers at distance.
The Grille appeared in two distinct variants during her short production life spanning 1943 into 1944. The type was based upon the chassis of the Czech Panzer 38(t) light tank though its turret was completely removed in favor of a three-sided, five-panel, open-air armored superstructure fitting the 15cm (150mm) schweres Infanteriegeschutz 33 series heavy infantry field gun. The superstructure featured armor thickness ranging from 10mm to 15mm. Both the top and rear facings of the superstructure were left open to facilitate the needed room in managing gun functions as well as ejecting spent 150mm shell casings or accepting fresh cartridges through the rear area. Some 493 total Grille vehicles were completed including accompanying ammunition carriers. 120 examples of the ammunition carrier variant were developed from existing Czech Panzer 38(t) tanks and needed to resupply Grille systems in-the-field for there was little to no stowage space aboard the tank for the required 150mm ammunition. The vehicle was defensed by a single 7.92mm MG34 general purpose machine gun and crewed by four personnel to include the driver, commander, gunner and loader. The driver was the only crewmember protected within the hull of the vehicle. As the superstructure was fixed to the top of the Panzer 38(t) roof, the entire vehicle would have to be turned into the direction of intended fire for the even the gun mount was limited in its traversal/elevation.
The first production variant was the Grille became the "Ausf. H" mark (based on the Czech Panzer 38(t) Ausf. H hull) and this was distinct from the follow-up production form in that it mounted the engine to the rear of the vehicle hull. The crew compartment was set low and towards the front area of the hull with the gun in front. The hull armor protection was 50mm thick along the frontal area and 25mm along the sides. The Grille "Ausf. M" variant (based on the Panzer 38(t) Ausf. M hull) moved the engine to the middle of the design and relocated the gun mount, superstructure and gunnery crew to the rear of the hull roof. Both versions were completed with the same field gun. Their suspension was leaf sprung and power derived from a single Praga AC 6-cylinder gasoline-fueled engine of 147 horsepower. This provided the mount with a top speed of 22 miles per hour and an operational range equal to 120 miles. The concern of BMM produced 90 Ausf. H models beginning in February of 1943 while the 282 Ausf. M models appeared beginning in April. All told, some 493 Grille gun and ammunition carriers were produced. The ammunition carriers were completed in such a way that they could be converted into the gun versions if needed.
The Type 33 heavy infantry gun utilized in the Grille design was developed back in the late 1920's and became one of the best artillery pieces of her day, becoming the standard German Army heavy gun of World War 2. The gun itself weighed in at nearly 4,000lbs when removed from the accompanying two-wheeled carriage. This weight, combined with the required armor protection, ammunition and the four crew grew the Grille's operating weight to 16,500 lbs (8.5 tons).
The Grille maintained some definite advantages and disadvantages in her design. The German Army could now field a 150mm field howitzer along battle fronts and transport her at speed compared to the slower, towed nature of the base Type 33 field gun. She also had the tactical ability to fire off a round and relocate to a new position in the "shoot and scoot" method, in effect, countering any expected return fire. Where the Grille design lacked was in its rather thin armor protection for the gunnery crew and in its open-toped superstructure arrangement. The open-air nature of the superstructure exposed the gunnery crew to battlefield elements such as small arms fire and battlefield spray as well as adverse weather conditions and direct assaults from enemy infantry.
The German Army used the 15cm sIG 33 Ausf. M to good effect in fire support missions alongside Panzer formations and infantry units throughout campaigns in Poland, France, Greece and the Soviet Union. Such systems proved cost-effective solutions that helped to extend the life of seemingly outdated military equipment.