Haber-Bosch Process and World War 1: How Chemistry From Air Replaced Saltpeter

The Haber-Bosch process is the industrial method of making ammonia from nitrogen in the air and hydrogen, which Fritz Haber and Carl Bosch scaled up to factory size between 1909 and 1913. In World War 1 it saved Germany from a "saltpeter famine": the British Royal Navy cut off Chilean saltpeter, the raw material for gunpowder and TNT, and by autumn 1914 it was clear that Germany's munitions would last only about six months. Synthetic ammonia from the Oppau and Leuna plants replaced the Chilean imports, and the German guns kept firing.

Why explosives depended on Chilean saltpeter

Every shell of the Great War was, at heart, a nitrogen compound. Nitroglycerin, guncotton and TNT are made by nitration, meaning treatment with nitric acid, and until the 1910s nitric acid came mostly from sodium nitrate, known as Chile saltpeter. The world's main deposit lay in the Atacama Desert: Chile became the global supplier of nitrogen for fertilizer and explosives after the War of the Pacific (1879-1883).

Chemists saw the problem long before 1914. In 1898 the Briton William Crookes warned that saltpeter reserves were running out and that the only way out was to take nitrogen straight from the air, where it makes up 78% by volume. Berlin had a second worry: Germany shipped Chilean saltpeter by sea, and the sea belonged to the British fleet.

1909-1913: from lab bench to factory

In 1909 Haber, with his colleague Robert Le Rossignol, produced ammonia from hydrogen and nitrogen. The reaction is reversible, so it needs a careful balance: at high temperature it runs fast but the ammonia breaks down again, at low temperature it nearly stalls. The answer was high pressure, heat and a catalyst. The research was funded by BASF, which assigned Carl Bosch to move the process from the laboratory into industrial reactors, while Alwin Mittasch found a cheap iron catalyst to replace scarce osmium.

The key numbers of the process:

• The patent was granted in 1910.
• Typical conditions: about 200 atmospheres and roughly 500 °C.
• The first large plant at Oppau near Ludwigshafen came online in 1913.
• Under the patent Haber received 1.5 pfennigs for every kilogram of ammonia.

The slogan of the era was "bread from air" (Brot aus Luft): for the first time fertilizer no longer depended on mineral deposits and bird droppings. But the same ammonia also led to explosives.

How it works in plain words

The equation is short: N2 + 3H2 ⇌ 2NH3 - one molecule of nitrogen and three of hydrogen make two molecules of ammonia. The nitrogen comes from the air, while the hydrogen at the plants of that era came from coal, so the process devoured energy: the more ammonia, the more fuel. That is why synthesis was tied to coalfields and big industrial hubs. Bosch also had to solve an engineering problem: the reactors had to withstand enormous pressure and hydrogen that eats into steel. It was as great a victory as the chemical discovery itself.

Autumn 1914: the blockade and a six-month stockpile

When the war began, the Royal Navy cut the sea routes from Chile, and in autumn 1914 it became clear that without new nitrates Germany would run out of munitions in about half a year. Haber became head of the chemistry department of Walter Rathenau's War Raw Materials Section, and the bet was placed on synthetic nitrogen. How the blockade itself worked is covered in the Battle of Jutland and the naval blockade.

The chain went like this: ammonia was oxidised to nitric acid, and nitric acid was turned into explosives, TNT among them. In 1917 an even larger plant, Leuna, began operating near Merseburg, and in the last year of the war Oppau and Leuna together produced about 115,000 tons of synthetic ammonia. This chemistry fed the artillery of World War 1, which fired millions of shells in a single battle.

How much this changed the war is debated. Some argue that without ammonia synthesis Germany would have run out of munitions within months and the war would have ended very quickly; others point out that such "what if" claims are only conjecture. One thing is beyond doubt: Haber and Bosch made the German army independent of Chilean saltpeter, and the blockade could not stop the supply of shells.

Haber: "bread from air" and "death from air"

They were the same man. On 22 April 1915 at Ypres Haber directed the first large-scale chlorine gas attack, described in the article on chemical weapons in World War 1. Soon afterwards, in early May 1915, his wife, the chemist Clara Immerwahr, took her own life; she had condemned the use of science to build weapons.

After the war the Allies put Haber on a list of war criminals and he briefly fled to Switzerland. Even so, the Nobel Committee awarded him the 1918 Prize in Chemistry "for the synthesis of ammonia from its elements" (presented in 1919), and Bosch received his own prize in 1931. In 1933, after the Nazis took power, Haber, who was of Jewish origin, left Germany and died in Basel in January 1934.

Legacy: from shells to fertilizer

After the war the Chilean saltpeter industry could not compete, and the Haber-Bosch process spread across the world, barely changed in a hundred years. By an estimate from the mid-2000s, more than 100 million tons of nitrogen are taken from the air every year and turned into fertilizer. That stands behind a sevenfold rise in world food production and a nearly fourfold rise in the Earth's population during the 20th century.

So the story from World War 1 has two sides: the same synthesis that gave Germany explosives has fed billions of people. For how the war changed life behind the lines, read the home front in World War 1, and for the money side, what World War 1 cost.

What this means for a Frontkrieg player

Frontkrieg has no separate "saltpeter" resource: the economy is built from seven resources in three categories - food, materials and energy. But the historical lesson is the same: a state holds out until its supply line is cut, and survives if it finds a substitute in time. In practice that means the following:

• A shortage is counted per category, not per single resource. A lack of coal can be covered by oil or gas, and a lack of grain by fish, so keep at least two sources in every category.
• A category shortage removes 15 points of province morale across the whole state. Do not let it get there: the guide to province morale in Frontkrieg shows how to raise it.
• A port adds +25% to a province's resource output and a railway adds another +10%. Invest in provinces with key resources before the enemy reaches them.
• Vehicles and fleets burn oil every day, so without an energy reserve the war grinds to a halt; details are in the Frontkrieg economy guide.

You can try your own "saltpeter" strategy for free in the lobby - a new match starts every day. More history and guides are in the blog.

FAQ

What is the Haber-Bosch process?

It is the industrial synthesis of ammonia from nitrogen in the air and hydrogen over an iron catalyst at roughly 200 atmospheres and 500 °C. Ammonia is the basis of nitrogen fertilizer and, through nitric acid, of explosives.

Why was saltpeter so important in World War 1?

It supplied the nitric acid for gunpowder, nitroglycerin and TNT. The main deposit was in Chile, and after the British blockade of 1914 Germany was cut off from that source.

Is it true that the war would have ended in 1915 without Haber?

That is conjecture, not established fact. What is known is that in autumn 1914 Germany, without new nitrates, would have run out of munitions in about six months, and synthetic ammonia closed that gap.

How much ammonia did Germany produce at the end of the war?

By one estimate, in the last year of the war the Oppau and Leuna plants together produced about 115,000 tons of synthetic ammonia.

Further reading: the Haber process on Wikipedia. Frontkrieg is a free game with no pay-to-win, available in four languages.