Man has always attempted to protect the valuable head from injury. Obviously the importance of the head was recognized even in prehistoric times. The caveman used the skins from his animal kills and placed the animal head over his own. He at least looked menacing to his enemies. This was adequate during the stone age, but when weapons became more substantial, the animal head was very little protection. During the Stone Age man learned to sharpen the tips of spears by subjecting the the weapon to a hot fire. These spears could easily pierce the head and heart with only animal skin protection for the body.
Our prehistoric ancestors then turned to the carcasses of animals and fish to afford a more substantial protection. Bones were used to build a more secure battle helmet that was not so easily penetrated by a sharp spear or axe. This was necessary because too many of the brave cave warriors had been knocked senseless by a spear to the head.
A more substantial battle helmet became necessary around 3000 to 3500 BCE when bronze smelting was developed in China. Bronze was a misnomer because 90% of the metal was copper, but by the next millennium bronze was the most dense metal the world had ever seen. Not everyone had access to the knowledge to develop bronze at the same time, therefore, those who did not possess the knowledge to produce the metal were overwhelmed by their more astute neighbors.
Bronze battle helmets were worn by the hoplite Greek army during many famous confrontations. King Leonidas wore a bronze helmet with a horsehair crest when they confronted the Persian Emperor Xerxes and the overwhelming Persian army in August 480 BCE. The place of this battle was called Thermopylae. It was one of the most courageous battles of the Greek democracy.
In the ancient ages of our world how knowledge spread was a very vital part of whether a culture, city-state or a nation survived. If an enemy knew the composition of metal smelting and they confronted a nation who was still wearing helmets of walrus tusk, the outcome was inevitable. At one time the one who had the best weapons and technology won, but is it still true today?
At one time in our existence the most formidable chariot won the battle. The number of soldiers involved in a battle was key to success. The best bomb was vital in the end of World War II. What is the winning element today?