By
Mike Cecil
Head of Military Heraldry and Technology
Australian War Memorial

During the 1950s, International Harvester Company in close collaboration with the Australian Army, developed a 2-1/2-ton 4x4 General Service truck.  Of the ‘cab-over-engine’ design, the initial prototypes underwent testing in the mid-1950s, followed by 100 improved trucks used for extended user trials in the late 1950s and early 1960s.  The culmination of this developmental process was the ‘Truck Cargo 2-1/2-ton GS with winch (Aust) No.1 Mk3’.  Delivery of the production models began in September 1963. Further development resulted in the 6x6 version, the ‘Truck, Cargo, 5-ton GS with winch, F1’ a few years later. 

Recognising that troops travelling in soft-skinned vehicles are very vulnerable to ambush, the Army Design Establishment (ADE) developed demountable armoured bodywork to fit both the 4x4 and 6x6 trucks.  This armoured bodywork was supplied to users in a ‘kit’ form. It was designated as an Armoured Protection Kit (APK)  to ‘….. provide some protection against small arms fire and explosive blast for troops travelling in these vehicles’. ¹

The APK consisted of several armour plate assemblies that fitted around the outside of the driving cabin, onto trapezoidal shaped frames mounted on the rear traybody to form a protected troop compartment, and along the sides adjacent to the fuel tanks. There was no additional overhead protection over the driving cabin or over the troop compartment. Once installed, the truck could carry and provide limited protection for an infantry Section in full battle order, or sixteen troops armed with personal weapons, as well as the driver and driver’s mate in the cabin. 

The protected troop compartment was assembled on the vehicle tray.   Three trapezoidal frames made from steel tube formed the supports for the armour panels. The four armour panels were mounted onto the existing cargo body hinges, and secured near the top of each edge with a sliding pin.  For rapid emergency exit, the pins could be pulled free and the armoured sides pushed out.

Normal entry and exit was through the two rear doors. Steps were hung centrally from the hinge brackets, and secured with clips to the vehicle chassis. Protection was also provided for the fuel tanks, in the form of a rectangular plate that hung from the lashing rings on the traybody, and brackets which protruded out from the standard fuel tank mounts.  Curiously, no protection was provided for the tyres, and the APK did not include the fitting of ‘runflat’ type tyres.

Installing the APK involved three phases.  The first required the permanent modification of the vehicle by the removal of such items as the cabin grab handles and the fitting of support brackets to the chassis. The front bumper and lashing rings on the traybody sides were also modified. These alterations were only to allow fitting of the APK, and did not alter the cargo capacity of the truck.

Phase 2 involved the removal of items such as doors, traybody sides, tailgate and canopy frame, and the brush guard from the front bumper.  Once these items were removed, the third phase - the actual installation of the APK - could commence.  Although a number of the individual panels were very heavy, the installation was a relatively straight forward task for an NCO and nine soldiers.

Several kits were deployed operationally to South Vietnam in mid-1967. 102 Field Workshops based at Vung Tau undertook the fitting of an APK to an International Mk3 4x4 truck during July 1967.  A number of problems were encountered, such as the APK being deficient some fastenings, and the tolerances of a number of parts being far too tight to allow easy installation. Panels, particularly the large cabin frontal armour, were simply too heavy to be manhandled, and required a crane. The phase 1 conversion took 10 hours to complete, while the actual installation in phases 2 and 3 took 60 hours!