At the same time when SAT built the new factory in Karis, the Finnish Defence Forces reported needing thousands of vehicles in the near future. SAT suggested building the factory larger in order to meet the demand. However, the importers of other makes as well as some politicians suspected that SAT tried to use the war to gain a dominant position in the Finnish market. Eventually, an agreement was reached in 1943 when SAT, the state and a number of Finnish companies set up a separate company Yhteissisu to produce lorries. SAT and Yhteissisu signed a contract about transferring Sisu S-21 lorry production to Yhteissisu. Vanaja municipality next to Hämeenlinna was selected for the factory location.