Bayonet, a short steel blade attached to the muzzle of a musket or rifle. The earliest type of bayonet was the plug bayonet, a steel dagger with a wooden handle that fit into the muzzle of a musket. It was developed in France around 1650, and most likely was named after the bayonnette, a dagger made in the city of Bayonne.

The great disadvantage of the plug bayonet was that the musket could not be loaded or fired while the bayonet was in place. This defect was remedied by placing a socket to hold the bayonet at the side of the muzzle. By 1700 the armies of Europe no longer needed pikemen—troops armed with long, spearlike weapons—to protect the musketeers as they reloaded, since the musketeers could defend themselves with their bayonets.

Throughout the 18th and 19th centuries the bayonet was standard equipment for foot soldiers, and was sometimes used in the last stages of an attack. The use of the bayonet decreased as rapid-firing rifles and machine guns were developed. It was still used, however, for some mass attacks in the trench warfare of World War I. Although it continues to be standard equipment, it is now rarely used in combat. U.S. Army troops are equipped with a bayonet whose primary function is to serve as a field knife.