37.1 KT3 - Radio, engines and mobile warfare, 1917-40

Enquiry Frame and Chronology

This Paper 3 depth key topic is about how technology changed the reality of warfare and how armies perceived that change. Do not turn it into a list of machines. The specification asks you to link three developments:

The key concept is operational mobility. Tactical mobility means movement on the battlefield: crossing trenches, wire, shell holes or local defensive positions. Operational mobility means moving and controlling forces over a wider area fast enough to disrupt the enemy's reserves, command system and strategic choices. Tanks helped with tactical mobility. Motor transport helped with operational mobility. Radio made both more controllable.

Keep this chronology in view:

The broad change from 1917 to 1940 was therefore not simply "better tanks". Cambrai and Amiens showed what engines could do when placed inside combined-arms attacks. The interwar question was whether armies would build their planning around speed, radio and concentration, or fit the new machines into older assumptions about controlled, firepower-heavy battle.

Cambrai, Amiens and the Engine

The internal combustion engine mattered because it gave armies new ways to move power across the battlefield. Steam engines had transformed railways and ships in the nineteenth century, but railways were tied to tracks and could be cut. Horses remained vital in 1914-18, but they were vulnerable, slow to supply and limited on shell-torn ground. Petrol-driven engines made aircraft, tanks, lorries, tractors and motorcycles possible. They did not remove mud, breakdowns or supply problems, but they opened possibilities that horse and foot armies could not provide.

The tank was the most obvious new engine-driven weapon. Its purpose was to cross trenches, crush wire and attack machine-gun positions. Early tanks were slow, hot, noisy and mechanically unreliable. They could terrify defenders, but they could also break down before reaching the enemy. Their significance was therefore not that they immediately solved trench warfare, but that they pointed towards a battlefield where protected movement might return.

Cambrai, beginning on 20 November 1917, was a major test. The British used more than 400 tanks in a surprise attack against the Hindenburg Line. The attack avoided the long preliminary bombardment that normally warned defenders. Artillery used predicted fire, infantry followed behind tanks, and aircraft supported observation and ground attack. The initial result was dramatic: German defences were penetrated in places, bells rang in Britain in celebration, and many observers saw proof that tanks could restore movement.

Cambrai also showed limits. Many tanks broke down or were knocked out. Infantry, cavalry, artillery and reserves could not exploit every opening. Communication remained difficult once the attack moved forward. German counter-attacks from 30 November recovered much of the lost ground. The battle's lesson was therefore double-edged:

Amiens on 8 August 1918 showed a more mature version of this idea. The Allied attack used secrecy, fog, artillery, infantry, aircraft, cavalry and hundreds of tanks. British, Australian, Canadian and French forces struck without a long warning bombardment. Aircraft helped observation, attacked troops and disrupted movement. Tanks helped crush wire and strongpoints. Motor transport helped move supplies and personnel in the rear. The result was a major German defeat and a collapse in morale among parts of the German army.

Amiens did not mean that the First World War had suddenly become fully mobile in the later 1940 sense. Tanks still broke down; many were disabled within the first day; cavalry could not transform the battle into a sweeping pursuit; and supply still limited exploitation. However, Amiens mattered because it showed that the answer to trench stalemate was not one weapon but a system: surprise, artillery neutralisation, armoured movement, air support, infantry skill, logistics and command.

Aircraft were part of the same engine revolution. In 1914 they were mostly used for reconnaissance. By 1918 aircraft observed artillery fire, photographed defences, attacked troops and transport, fought for control of the air and helped commanders understand enemy movement. Aircraft made mobile warfare more dangerous because concentrations of troops, bridges, roads and columns could be seen and attacked. They also made mobility more possible because commanders could receive information from beyond the front line.

Motor transport was less glamorous than tanks or aircraft, but it was essential. Lorries, tractors and cars moved ammunition, food, fuel, engineers, staff officers and reserves. A tank attack without fuel, spare parts and recovery equipment soon stopped. An aircraft force without mechanics, petrol and replacement parts could not fly. By 1918, the lesson was clear: the internal combustion engine mattered most when armies treated mobility as a whole system of fighting, observing, supplying and commanding.

Radio and Control

Radio mattered because mobile warfare created a command problem. If forces moved faster than messengers, telephone cables or visual signals, commanders could lose control of the battle. In trench warfare, armies could often lay telephone lines between fixed positions, although shellfire frequently cut them. In mobile warfare, cables could not keep up. Runners, flags, signal lamps, pigeons and dispatch riders all had uses, but each had obvious limits.

Wireless communication during the First World War was already important, especially in aircraft and artillery cooperation. Aircraft could observe shell bursts and send corrections to artillery batteries. Wireless could also report enemy movement or help headquarters gather intelligence more quickly than older methods. At sea, radio had long been vital for ships. On land, however, early sets were heavy, fragile, short-ranged and vulnerable to interference. They also required trained operators and secure procedures.

The tank made the problem sharper. A tank was a moving steel box. Once it crossed no man's land, it could not easily receive orders by telephone. Crews had poor visibility and deafening conditions inside the vehicle. Some later First World War tanks and command tanks used wireless, flags or other signals, but communication remained crude. This limited exploitation: commanders might know a battle had begun, but not exactly where tanks had reached, where infantry were stuck, or where reserves should be sent.

Radio's significance can be summarised like this:

The implication for mobile warfare was profound. The army that could keep armoured units, motorised infantry, artillery, aircraft and headquarters connected could move faster without dissolving into confusion. The army that relied mainly on fixed-line communications and centralised orders would struggle once the front broke open.

This does not mean radio removed uncertainty. Radio messages could be misunderstood, intercepted or jammed. A fast-moving commander could also use radio to ignore orders or create a crisis by racing ahead. But compared with cable-bound command, radio allowed a different tempo. Orders, reports and requests for support could travel while units were moving. In 1940 this difference became one of Germany's advantages. Many German tanks had radios, and panzer commanders could coordinate movement more flexibly. French armoured units often had fewer radios and were used inside a command system that expected deliberate planning and written orders.

Radio therefore changed warfare less as a gadget than as a nervous system. The internal combustion engine gave armies muscles; radio gave them a chance of coordination. Without that coordination, mobility could produce traffic jams, isolated spearheads and missed opportunities. With it, speed could become operational shock.

French Planning and Gamelin

France did not ignore modern technology in the 1930s. That is a common but misleading story. France had a large army, significant artillery, good tanks in several categories, motorised formations, aircraft and the Maginot Line. Some French tanks, such as the Char B1 bis and Somua S35, were heavily armoured and in some respects technically formidable. The problem was how those resources were organised and controlled.