In August 1914 every army in Europe expected a short war of movement. Within four months the Western Front had frozen into a line of trenches from the North Sea to Switzerland, and for the next three and a half years it moved almost not at all — while millions of people died trying to move it. That is not a story about courage or stupidity. It is a story about arithmetic that nobody in 1914 had done, and this page does it: how fast an attack can advance, how fast a defender can send help, what a week of shellfire actually achieves, and what a metre of ground cost.
Drag the timeline. It begins on the day Franz Ferdinand was shot and ends at the armistice, and every country changes colour on the date it actually entered. For the first five weeks you are watching the July crisis, where each declaration is an obligation discharging rather than a decision being taken — the arrows show them. After that, watch how much later the rest arrives: Italy nearly a year in, Romania two, the United States almost three. Switch to the world view and the name of the thing stops being a figure of speech.
Here is the whole Western Front in one race. An attacking infantryman crosses broken ground on foot, under fire, dragging his own supplies — and every metre he takes has to be consolidated before the next. A defender who sees the attack coming sends reserves to the threatened point by train, on rails already built, behind his own lines. Set the two speeds and watch. The bar underneath shows who reaches the breach first. There is no setting of these sliders, within anything the technology of 1916 could do, where the attacker wins — and that is what a stalemate is.
Before the Somme the British fired something like a million and a half shells over seven days onto a front of 25,000 yards. Divide one by the other and it sounds unanswerable. Then take away the shrapnel rounds, which burst in the air and were nearly useless against barbed wire and deep dugouts, and take away the shells that simply did not go off — the dud rate is disputed but was certainly bad. What is left is the number that actually mattered, and on 1 July the wire in many places was still there. Move the sliders and watch the impressive number become the real one.
These are the three long battles of the Western Front, with the ground each one gained at its deepest point and the casualties on all sides. The final column is the division: people per metre. It is a grotesque way to measure a battle and it is exactly how the people planning them came to think, which is the point. Note that Verdun ends where it started — the French recovered almost precisely the ground they had lost, so the denominator is nearly zero and the ratio is not defined at all.
| Battle | Days | Deepest advance | Casualties, all sides | Per metre | Per day |
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Everything above this line is a mechanism you can move a slider on. This part is not, and it should not be. Between 15 and 22 million people died in the First World War: somewhere between 9 and 11 million of them soldiers, and between 6 and 13 million civilians, mostly of starvation, disease and displacement rather than of shells.
The width of those bars is not sloppiness. It is what happens when empires collapse before anyone counts, when the same death is recorded twice or not at all, when the 1918 influenza pandemic kills tens of millions across a world already too broken to keep registers, and when successor states have reasons to prefer a larger or a smaller number. Historians argue about the totals to this day, and a source quoting a single exact figure to the nearest thousand is telling you more about its own confidence than about the war.
One number from section 4 is worth holding onto on its own. On 1 July 1916, the first day of the Somme, the British Army suffered 57,470 casualties, of whom 19,240 were killed. Spread across the daylight hours of that single day, that is about one and a half people every second, from breakfast until dark.
The mechanisms are computed. The race in section 2 solves the two travel times directly and the ratio between them; at the historical settings a defender moving reserves by rail covers ground about 13,500 times faster than the Somme advanced, which is why the front did not break. Section 3 divides shells by frontage and then by the share that was high explosive and did explode. Section 4 divides casualties by metres. You can check every one of these on paper.
The inputs are quoted, and they are contested. The Somme bombardment is usually given as between 1.5 and 1.7 million shells over roughly 25,000 yards; the dud rate is genuinely disputed and the slider deliberately spans the argument rather than picking a winner. Casualty figures for every battle here vary between sources by tens of thousands, and the deepest-advance figures compress a messy, uneven front line into one number. Where a range exists this page shows the range.
A word about the map, because it is lying to you in a way worth knowing. The outlines are Natural Earth 1:110m, which is public domain, and they are modern borders — the only country data that exists. But three of the powers that fought this war no longer exist. Austria-Hungary is drawn here as Austria, Hungary, Czechia, Slovakia, Slovenia, Croatia and Bosnia; the Ottoman Empire as Turkey and much of the Levant and Arabia; the Russian Empire as Russia, Ukraine, Belarus, the Baltic states, Moldova and Finland. Poland is left uncoloured throughout, because in 1914 there was no Poland — it had been partitioned between Germany, Austria-Hungary and Russia, and Poles fought on both sides. Serbia is shown with Kosovo and North Macedonia, which it then governed. So the shapes are approximately where the fighting powers were, and are definitely not what any map of 1914 looked like. That the borders of Europe were redrawn this completely is itself one of the war’s largest results.
And a caution about the whole exercise. Arithmetic explains why the line did not move. It does not explain why the war began, why it continued after it was obviously deadlocked, or why men climbed out of the trenches when ordered to. Those are questions about politics, empire, obligation and fear, and no slider on this page touches them. Treat what is here as one honest tool among many, and not as the account. Every number on this page was a person.