The Battle of Verdun, the longest engagement of World War I, ends on this day after ten months and close to a million total casualties suffered by German and French troops.

The battle had begun on February 21, after the Germans—led by Chief of Staff Erich von Falkenhayn—developed a plan to attack the fortress city of Verdun, on the Meuse River in France. Falkenhayn believed that the French army was more vulnerable than the British, and that a major defeat on the Western Front would push the Allies to open peace negotiations. From the beginning, casualties mounted quickly on both sides of the conflict, and after some early gains of territory by the Germans, the battle settled into a bloody stalemate. Among the weapons in the German arsenal was the newly-invented flammenwerfer, or flamethrower; that year also saw the first use by the Germans of phosgene gas, ten times more lethal than the chlorine gas they previously used.

As fighting at Verdun stretched on and on, German resources were stretched thinner by having to confront both a British-led offensive on the Somme River and Russia’s Brusilov Offensive on the Eastern Front. In July, the Kaiser, frustrated by the state of things at Verdun, removed Falkenhayn and sent him to command the 9th Army in Transylvania; Paul von Hindenburg took his place. By early December, under Robert Nivelle, who had been appointed to replace Philippe PÉtain in April, the French had managed to recapture much of their lost territory, and in the last three days of battle took 11,000 German prisoners before Hindenburg finally called a stop to the German attacks.

The massive loss of life at Verdun—143,000 German dead out of 337,000 casualties, to France’s 162,440 out of 377,231—would come to symbolize, more than that of any other battle, the bloody nature of trench warfare on the Western Front.