As part of Britain's slow rearmament program during the mid-1930s, Morris was tasked with swiftly developing an interim armored car design. Based on its C8 Commercial 4×2 truck, the chassis was lengthened and an armored, riveted hull mounted. Armament was either a Boys AT rifle and Bren LMG or a Vickers 7.7mm MG in a two-man, open-topped turret. The vehicle was also equipped with a No.19 radio set.
Tested in 1936, the Ministry of Defence placed an order for around 100 CS9s, which were duly delivered during 1938. The Morris CS9 equipped the 12th Royal Lancers – the only armored car regiment with the BEF in France 1940. 38 were in service during the Battle of France, with all being lost.
11th Hussars took 30 Morris CS9 armored cars to the Western Desert, where they gave good service. By late 1941/42, their armor and armament was insufficient against new Axis designs, and they were retired to second-line duties.