Already the very first production lot of Sisu S-323's included customised lorries for the Finnish Defence Forces. During the Second World War lorry production was transferred to another company, Yhteissisu, which was set up to produce lorries and buses for the military. In 1958 the Defence Forces arranged a thorough test trial comparing lorries of different producers; these tests gave the Sisu K-26, modified from a civil model, a good rating. In 1959 SAT introduced Kärppä-Sisu K-35 for military use but 4×2-driven. Production of military off-road vehicles started in 1964 when SAT presented KB-45, a new light 4×4 lorry. The military vehicle production was moved from Karis to Hämeenlinna when the upgraded A-45 was presented. Medium heavy SA-150 and heavy 6×6-driven SA-240 production followed after. SA-110 was a light lorry prototype which was only produced six units. In 1990 the demining vehicle RA-140 was introduced and they were produced a small series starting from 1994.