Which signaling methods were still used by armies on the eve of World War II?

On the eve of World War II, armies utilized a diverse array of signaling methods, ranging from traditional physical messengers to emerging electrical technologies. While radio and wire systems were becoming standard, older methods remained in active use to ensure communication redundancy and reliability.1

Signaling Methods Used

• Messenger Systems: Armies continued to rely on various forms of messenger service, including foot, mounted, motorcycle, automobile, and airplane couriers. Homing pigeons and messenger dogs were also employed as reliable, albeit slower, means of communication.1
• Visual Agencies: Visual signaling remained a critical component of battlefield communication. This included the use of flags, signal lamps (including blinker-light signaling), pyrotechnics, rockets, and Very pistols. Specialized panels were also laid out in open fields to communicate prearranged designs to aircraft.1
• Electrical Agencies: Wire-based systems provided the backbone for telephone and telegraph services, including the use of printing telegraphs (teleprinters). Both radiotelegraphy and radiotelephony were widely used, though radiotelephony was still considered less reliable for tactical purposes at that time.1

Naval and air forces also utilized these methods, with navies relying heavily on radio and blinker-light signaling, while air forces integrated radio and wire to coordinate between bases and aircraft.1