A small experimental unit had been experimenting with ground-attack tactics since 1937, initially in outdated biplanes such as the Potez 25, then in ANF Les Mureaux 115 monoplanes. Eventually, the "Armée de l’Air" concluded that low-altitude level-bombing was more suitable than dive-bombing for engaging enemy vehicles and artillery over the battlefield. The chosen tactic consisted in a nap-of-the-earth approach at maximum speed, followed by a strafing run or the delivery of time-delayed bombs directly over the target. French commanders widely considered this tactic as safe for the attackers, as anti-aircraft weapons then in service would be inefficient. The French Army was not using anti-aircraft autocannons at the time (the 25 mm Hotchkiss and 20 mm Oerlikon cannons were issued only later), relying instead on rifle-calibre machine guns and slow-firing 75 mm (2.95 in) guns.