Helmets were among the oldest forms of combat protection, and are known to have been worn by ancient Greeks, Romans, throughout the Middle Ages, and up to the end of the 1600s by many combatants. At that time, they were purely military equipment, protecting the head from cutting blows with swords, flying arrows, and low-velocity musketry. Some helmets, in order to protect the neck as well, have a sort of extension made of leather strips called pteruges, particularilly common in the Middle East. They were initially constructed from leather, and then bronze and iron during the Bronze and Iron Ages, but soon came to be made entirely from forged steel in many societies after about 950A.D. Military use of helmets declined after 1670, and rifled firearms ended their use by foot soldiers after 1700. By the 18th century, cavalry units often wore steel body cuirasses, and frequently metal skull protectors under their hats, called "secrets". The Prussian spiked helmet, or Pickelhaube, offered almost no protection from the increased use of heavy artillery during World War I, and in 1916 was replaced by the German steel helmet, or Stahlhelm, and afterwards it was worn merely for tradition.
The Napoleonic era saw ornate cavalry helmets reintroduced for cuirassiers and dragoons in some armies; they continued to be used by French forces during World War I as late as 1915, when they were replaced by the new French Adrian helmet. It was soon followed by the adoption of similar steel helmets by the other warring nations.
World War I and its increased use of heavy artillery had renewed the need for steel helmets, which were quickly introduced by all the combatant nations for their foot soldiers. In the 20th century, such helmets offered protection for the head from shrapnel and spent, or glancing, bullets.
The use of protective helmets by millions of fighting men in the two world wars increased awareness of "hard hat" protection. By the 1950s, hundreds of new applications for helmets were found. The helmet offered an unexpected advantage: Symbolism. It can signify that, like a soldier, the wearer is someone qualified for or capable of a certain task or activity, such as construction, operation of heavy machinery, or participation in certain sports.
Today's militaries often use high-quality helmets made of ballistic materials such as Kevlar, which have excellent bullet and fragmentation stopping power. Some helmets also have good non-ballistic protective qualities, though many do not. Non-ballistic injuries may be caused by many things, including (but not limited to) concussive shockwaves from explosions, motor vehicle accidents, or falls.
