The MA 51 rolling stock was a result of research conducted by the Compagnie du chemin de fer métropolitain de Paris (CMP) and the Régie Autonome des Transports Parisiens (RATP) during the 1940 in response to the then-used Sprague-Thomson rolling stock being considered heavy and outdated.
At the same time, the company also desired to have circulating modular trains so that they may have been expanded during peak hours.