The British offensive on the Somme began on July 1, 1916. After 20 weeks, they had advanced six miles. The German line retreated, but was not broken. The horrifying casualties were shared equally between the two sides: 300,000 men died. Bloodier battles would come in 1918, but on the first day of the Somme the British Army suffered its greatest daily loss: 19,000 killed.

Coming at the mid-point of World War I, the Battle of the Somme is often taken to exemplify the stupidity of the war on the western front. But this terrible experience took place at a unique moment, defined by two facts.

On the one hand, Britain’s deployment of military manpower was nearly complete. On the other, the deployment of British firepower had barely begun. Firepower was produced by the economy, and it was this mobilisation of economies that would eventually decide the war.

To illustrate, Figure 1 below compares July 1916 (as the British offensive unfolded on the Somme) to February 1918 (before the German spring offensive of that year).

Over this period, the number of British and Empire soldiers on the western front rose by 30% (from 1.4m to nearly 1.9m). Over the same period, the shell stock of the British army in France grew by an enormous 150% (from 6.5m to 16.5m shells), while the home stockpile grew more than ten times (from 1m to 11m).

After the Somme the British army was supplied with vastly more firepower than before. There was a revolution of variety as well as of quantity. And it was firepower, rather than manpower, that would decide the course of this war.

Firepower

Source: Bruce Bairnsfather, Fragments from France (The Knickerbocker Press, 1917). Courtesy of Major and Mrs Holt. , Author provided

This is because the military technologies of 1914 – earthworks, barbed wire, heavy machine guns, and artillery – embedded the defender.

Facing these, the attacking soldier had a rifle. He could fire standing up, making him an easy target, or lying down, meaning he could not move. He could get up and move only if supporting shellfire of heavy guns from behind would stop the enemy shooting back. But, if the shellfire did not destroy the enemy line completely, the attacking infantryman would be cut down in the second after the shelling stopped. This is what happened on the first day of the Somme.

For the infantryman to be able once again to fire and move at the same time required new kinds of armament: light automatic weapons, rifle grenades, trench mortars, and the supporting fire of tanks and aircraft. These were available in significant quantities only after the Somme.

The statistics of British war production bear this out (Figure 2 below). The Somme offensive divides the war into two equal halves. After the mid-point, the British economy supplied guns and rifles at twice to three times the rate before; for shells, it was more than five times, and for the volume of explosives more than six times. For newer types of weaponry, the figures are also striking. After the Somme, trench mortars were delivered at four times the rate before; for machine guns the ratio was nine times, for engines and aircraft and engines eight and nine times respectively, and for tanks 34 times.

Notably, the British economy and its workforce supplied these tremendous increases at the same time as giving up young men to cover military losses and expand the army in the field.

A question of money and time

While the British economy grew, the German economy shrank. German war production increased, but less rapidly than in Britain, and least in the most innovative branches of war production: aviation and armour. Germany could not supply the war without incurring widespread shortage and hunger. And Germany’s economy was industrially the most developed of the Central Powers alliance. Germany’s poorer allies were even less able to mobilise their young men, factories, and food resources.

Britain was initially the leading industrial power among the Allies. Then in 1917 they lost Russia, a poor country with a failing state, and won the support of the world’s largest and richest industrial country, the United States. By 1918 the Central Powers faced a coalition that represented two-thirds of the world’s prewar production and population. Taking the war as a whole, the Central Powers supplied their armies with more guns and almost as many rifles as the Allies (as Figure 3 shows). But more significantly, in supplies of machine guns and aircraft they fell short of the Allies by a half, and their production of tanks was negligible.

It was the mobilisation of the Allied economies that transformed Allied military power and enabled Allied soldiers to break the deadlock on the western front. But most products of the mobilisation reached the battlefield only after the Somme offensive had come to an end.

In The Pity of War, Niall Ferguson described the gradual mobilisation of the Allied economies as an “advantage squandered”. In The Economics of World War I, Stephen Broadberry and I responded: “Total war takes time.” The devastating losses of the Somme are explained by military mistakes and failures to learn, and by the time taken to mobilise production. This lesson was learned: when the next war came, the British economy would be fully mobilised in two years, not four.