A fighter capable of mounting a cannon was suggested by Georges Guynemer at the end of 1916. By raising the propeller above the cylinder heads, a 37mm Puteaux cannon with a shortened barrel was adapted to fire through the aircraft's hollow propeller shaft. The airframe of the SPAD XII was based on the smaller SPAD VII. In the cockpit, Deperdussin elevator and aileron controls were mounted on either side of the pilot because the cannon breech was between his legs. Due to this arrangement, the average pilot found the aircraft difficult to fly. In addition, the single-shot cannon was difficult to load and aim in air combat. When fired, it produced a heavy recoil and filled the cockpit with smoke and fumes. In spite of these problems and a troublesome geared Hispano-Suiza engine, Guynemer and René Fonck both scored victories with the SPAD XII. Although the Aviation Militaire initially ordered a thousand aircraft from the factory, no more than twenty were probably built. The order was cancelled in favor of the SPAD XIII.
One SPAD XII was assigned to American ace David Putnam of the 139th Aero Squadron. Upon his death, it was assigned to Charles Biddle of the 13th Aero Squadron.
"The machine I mention is the only one of its kind in the American service, so I am very anxious to try it out. They gave it to me when Putnam was killed. Guynemer had one and Fonck and Deullin each have one, and have used the with fair success. . . This special gun is difficult to use, but if a shot ever hits a Hun he might just as well say his prayers and give up, if he has time to think about anything at all." Charles Biddle, 13th Aero Squadron
"...the first time I used it [the cannon], it threw my motor out of order." Armand de Turenne, Escadrille SPA12