In the 1970s, when the General Staff of the Brazilian Army wondered what to do with its fleet of 350 Stuarts M3A1 / A3 acquired in the USA from 1942 (20) and the rest in 1944-45, the usual answer would be to find the nearest junkyard or throw it away for future collectors and museums. Many had already been stored, retired or cannibalized to keep about a hundred in operation. However, the Engesa company had already demonstrated that it could update the M8 Greyhound from the same time in an updated armored car, the Cascavel. In addition to purchasing a cheap and powerful armored car, Cascavel gave excellent returns in the export market. However, first of all, the motivation for upgrading the venerable Stuart was due to the lack of spare parts for these tanks. In fact, in 1977, Brazil had denounced the US-Brazil military agreements, interrupting all possible parts purchases. The Army gave technical supervision of the project to the Brazilian Army's Research and Development Center, and a manufacturer was chosen. The concept later evolved into a machine quite different from the original Stuart. The relative success of the project finally gave Bernardini the confidence to start his own main battle tank, the MB3 Tamoyo, in 1983.