World War I saw the crumbling of empires, and among those to collapse was the Russian empire of Czar Nicholas II. When Nicholas declared war against Germany and Austria-Hungary in July 1914, he was absolute ruler of a realm of nearly 150 million people that stretched from Central Europe to the Pacific and the edge of Afghanistan to the Arctic.

Less than three years later, in March 1917, after soldiers in Petrograd joined striking workers in protest against Nicholas’ rule, the czar was forced to abdicate. The following July, he and his family were herded into a cellar by Bolshevik revolutionaries and shot and stabbed to death, ending the Romanov dynasty’s three centuries of rule. Soon, amid the ruins of the Russian empire, the Soviet Union arose to become a world power.

Whether World War I was a game-changer that caused the Russian Revolution, or only hastened the inevitable collapse of an outdated monarchy unsuitable to compete in the modern world, is a question that historians continue to debate.

“Russia was more unstable, and had more serious internal dilemmas than many other great powers, and so the degree to which the shock of war resulted in chaos was correspondingly more intense,” explains Steven Miner, a history professor at Ohio University who specializes in Russia, the Soviet Union and Eastern Europe. “Collapse minus war was possible, but in my view not certain. Involvement in the cataclysm of war made it nearly inevitable.”

Prior to the war, Russia was at a crucial crossroads. “Some argue that Russia was slowly evolving more modern political and social institutions, that it had a vibrant culture, a highly educated elite, that it had survived the upheaval of the 1905 revolution, and that it had the fastest-growing economy in the world before 1914,” Miner says. But as he notes, the Czarist regime faced plenty of threats to stability, from dire urban working conditions to labor strife that the Czar’s soldiers tried to put down by massacring gold miners in Siberia in 1912. To make matters worse, Nicholas II was starting to roll back the limited democratic reforms that he had agreed to in 1905.

The antiquated czarist regime’s determination to hang onto power hindered modernization efforts, as a result, “the Russian Empire trailed behind the rest of Europe in terms of economic and industrial strength,” says Lynne Hartnett, an associate professor of history at Villanova University and an expert on the Russian Revolution.

That made Russia vulnerable in a war, because its factories simply couldn’t produce enough arms and ammunition to equip the Czar’s 1.4 million-man army. At the start of the war, the Russians had 800,000 men in uniform who didn’t even have rifles to train with, and those who did often had to make do with obsolete weapons that were nearly 40 years old, according to Jamie H. Cockfield’s 1999 book, With Snow on Their Boots. Some soldiers had to go into battle unarmed, until they could pick up a rifle from another soldier who had been killed or wounded. And Russia’s output of bullets initially was just 13,000 rounds a day, so they had to make every shot count.