While often overlooked, the stirrup is one of the most consequential inventions in military history. Before its invention, riders had to grip the horse with their legs, making it difficult to use weapons effectively without falling off. The earliest stirrups were likely loops of rope used in India for the big toe, but the metal foot stirrup appeared in China around the 4th century CE. This simple device allowed a rider to stand up in the saddle, providing the stability needed to shoot arrows with precision or charge with a heavy lance. It transformed the cavalry from a scouting unit into a dominant shock force on the battlefield. The stirrup spread through Central Asia to the West, eventually making the medieval knight possible. Some historians, like Lynn White Jr., argue that the stirrup was a primary catalyst for the development of feudalism in Europe, as it created a need for a specialized class of mounted elite warriors.