Developed to serve the same battlefield function as the classic American M113 Armored Personnel Carrier (APC), the Saurer 4K 4FA was adopted by the Army of Austria during the Cold War. The vehicle was designed and developed by the local concern of Saurer-Werke and was the further evolution of the design begun in the mid-1950s. The 4K 4FA introduced a 250 horsepower engine and entered service in 1961 with final deliveries (totaling 450 vehicles) in 1968. The line was succeeded in Austrian military service by the Steyr 4K 7FA G127 model of similar form and function though still retained an active presence in its ranks. Indeed even the 2001 introduction of the Ulan (ASCOD) tracked Infantry Fighting Vehicle (IFV) did not overtake the 4K 4FA line completely - the two serving side-by-side.
The 4K 4FA was given a low profile hull with shallow glacis plate and flat hull roof line. The hull sides angled slightly inwards for basic ballistics protection. The turret ring was installed over front-centerand the powerpack at front-right - leaving the driver's position along front-left. The other crewman required managed the turret armament and served as vehicle commander. Passenger seating totaled eight with protection from small arms fire and artillery "spray". The vehicle displayed a running length of 5.4 meters, a width of 2.5 meters and a height of 2.1 meters. Weight was in the 15 ton range. The one-man, power-assisted turret installed a 20mm Oerlikon Contraves Model 204 GK autocannon or a 12.7mm Heavy Machine Gun (HMG) depending on model in focus.
Interestingly, the 4K 4FA design was not completed with an inherent amphibious capability nor did it showcase standard Nuclear, Biological, Chemical (NBC) protection for its crew and occupants - rather standard qualities of any armored vehicle intended to operate in the European battlezone.
The running gear included five double-tired roadwheels to a track side, the drive sprockets at front and the track idlers at rear. Two track return rollers were used for each hull side and the suspension system was comprised of a torsion bar arrangement. Power was delivered through an in-house Saurer 2P 6-cylinder diesel unit outputting 250 horsepower. This provided for road speeds of up to 65 kph and a range out to 370 kilometers.
Operators of the 4K 4FA (beyond the Austrian Army) have included Bolivia, Greece (the ELVO "Leonidas") and Nigeria. Greek Army versions have been updated to the Leonidas II standard.
The 4K 4FA model line produced a handful of related variants led by the 4K 4FA-G1 with its 12.7mm machine gun turret armament and the 4K 4FA-G2 with its 20mm autocannon armament. 4K 3FA Fu1 served as a brigade-level command post vehicle while the 4K 3FA FuA was an artillery command post vehicle. The 4K 3FA Fu/F1A served in the anti-aircraft command post role and the 4K 4FA-Fs was a wireless teleprinter vehicle. 4K 4FA-San was an armored battlefield ambulance and 4K 4F GrW1 was the 81mm mortar carrier form.