CZK - SOŽ

In a decree issued by the Ministry of National Defence on 4 September 1950, the Headquarters of the Engineer Army commissioned the development of a heavy amphibious vehicle. The program was referred to as VOŽ (Large Amphibious Vehicle). In the early stages of this program, the sponsors had the idea that it would be a three-axle amphibious vehicle using the Tatra 111 chassis. The vehicle was to be of similar design to the American DUKW. It was to be a vehicle capable of carrying a load of 3-4 tons, or a 75mm cannon with ammunition and crew. The VOŽ programme was transformed into a pair of design proposals in 1951, namely a four-axle wheeled vehicle VOŽ-1 and a tracked vehicle VOŽ-2. In 1954, it was decided that the GVW would be a tracked vehicle.
However, the VŽV continued to explore the possibilities of developing a wheeled amphibious vehicle. It relaxed the specifications originally required and explored the possibility of using a truck chassis V3S. Approval for the SOS project was not granted until 11/1953. The program started on 14/1/1954 and the Automobile and Tractor Administration (ATS) was the designated authority. A lifting capacity of 2000 kg was required, later increased to 3000 kg (25 men or 100mm gun vz.53 or truck Tatra 805). A lengthy haggling ensued over competencies, vehicle form, etc. Automobilove závody Klementa Gotwalda n.p. (Praga) was commissioned to work on the project. The enterprise started working on the project from 1.1.1955, by 15.6.1955 it had to submit a preliminary design, which had to be approved by 10.7.1955. The final design was to be submitted by the end of the year and the prototype was to be delivered by 31.10.1956. Despite a slight delay, the submitted design was approved, but there was a requirement to use the new chassis of the contemplated replacement for the V3S trucks. AZKG's development efforts were concentrated on the development of the new truck and the SOŽ project was losing priority. Due to insufficient capacity, the work on the SOŽ was stopped by the decision of the Central Committee of the Communist Party of the Czechoslovak Communist Party of 12 December 1955. The originally required numbers of 2000-3000 pieces of amphibious vehicle of this category were to be filled by import of Soviet BAVs.
Army officials did not share this decision very much and on 30.1.1956 the Chief of the VŽV ordered an analysis comparing the SOŽ project with the Soviet BAV. The SOŽ was the more suitable adept for production and inclusion in the armament. On 20.3.1956 a request was made to reconsider the decision to discontinue the SOŽ program. After considerable effort, it was decided in 1957 to resume development work on the SOŽ, but to use the new chassis of the 3.5 tonne chassis truck under development Praga S-360. Even in view of the anticipated performance of the new truck, new and more demanding specifications were set. The vehicle was to be all-wheel drive with the option of disabling the front axle drive. It was to have central tyre compaction, a 150 hp engine. The vehicle was to carry 28 soldiers with equipment and armament or a three-ton load. The cruising speed was to be in the range of 10-12 km/h, on the road it was to reach a top speed of 80 km/h. The vehicle was to be armed with one 7.62mm machine gun. A production of 300 of these vehicles was required. Based on these requirements, a new development card No.1-31 was established on 12.3.1958. According to the plans, the first vehicles were to be delivered to the troops in 1963/64.
Unfortunately, a parallel programme of development of an armoured personnel carrier SKOT was underway, which was initially intended to use the same S-360 chassis. Due to the priority pursuit of the SKOT programme, the capacity for the development of the S-360 was exhausted and therefore the S-360 programme was not included in the development plan for the following years by decision of the MNO on 14 November 1959. Thus, amphibious vehicle needs in the following years were filled by deliveries from the Soviet Union.

Mgr.Martin Dubánek - Od bodák po tryskáče - Nedokončené Československé zbrojní projekty 1945-1955, Mladá fronta 2011, ISBN : 978-80-204-2515-7
Mgr.Martin Dubánek - Medium Amphibian SOŽ, ATM No.3/2013, ISSN: 1802-4823