In the 16th and 17th centuries light, open helmets with broad brims became popular. In the 18th and 19th centuries, with the growing effectiveness of firearms and the consequent decline in use of the sword and spear, helmets largely disappeared except for the use of light helmets by cavalry. The steel helmet reappeared, however, as a standard item for infantry in the opening years of World War I because it protected the head against the high-velocity metal fragments of exploding artillery shells. The French first adopted the helmet as standard equipment in late 1914 and were quickly followed by the British, the Germans, and then the rest of Europe. The modern infantry helmet is a smoothly rounded hemisphere designed to present glancing surfaces off of which bullets or shell fragments will bounce without imparting their full impact. The typical helmet is a hardened-steel shell with an inner textile liner and weighs about 1 to 4 pounds ( to kg).
A new technology called electric reactive armour (also termed electromagnetic reactive armour , or colloquially as electric armour ) is in development. This armour is made up of two or more conductive plates separated by an air gap or by an insulating material, creating a high-power capacitor .      In operation, a high-voltage power source charges the armour. When an incoming body penetrates the plates, it closes the circuit to discharge the capacitor, dumping a great deal of energy into the penetrator, which may vaporize it or even turn it into a plasma , significantly diffusing the attack. It is not public knowledge whether this is supposed to function against both kinetic energy penetrators and shaped charge jets, or only the latter. This technology has not yet been introduced on any known operational platform.
The Ottoman Empire used mail armour as well as mail and plate armour, and it was used in their armies until the 18th century by heavy cavalry and elite units such as the Janissaries. They spread its use into North Africa where it was adopted by Mamluk Egyptians and the Sudanese who produced it until the early 20th century. Ottoman mail was constructed with alternating rows of solid links and round riveted links. The Persians used mail armour as well as mail and plate armour. Persian mail and Ottoman mail were often quite similar in appearance.