The first prototype for Japanese samurai armor came about in the form of the yoroi during the Gempei War of 1181-1185. The weight of the yoroi was around 60lb. The upper-body armor of the samurai was known as the 'Do'. This comprised of the 'Sode', the suspended shoulder and upper-arm protection plates. The Sode had hoops by which silk cord was tied and then fixed to the back of the armor in an 'agemaki' / decorative knotted tassel. Guards were also placed over the shoulder cords, and a leather plate placed across the bow cords to prevent them from been cut or becoming ensnared during a skirmish.

A samurai's protective helmet, or Kabuto typically consisted of from eight to a dozen plates all fixed together with cone shaped bolts. Much like in the military of other cultures, a samurai's helmet would display the samurai's rank and his group or clan, and often be very elaborate and decorative looking. As many samurai had long hair, their ponytails would protrude through the tehen, a gap left in the centre of the helmets crown.

Shikoro is the name of the thick five-plated protector of the back of the head, neck and the cheekbone which was fastened to the bowl of the helmet. The top four plates of the Shikoro would be upturned to create the fukigaeshi. The idea of the fukigaeshi was to prevent the vertical slicing of the shikoro's horizontal fastening chords. A visor is also on the front of helmet and is known as the mabisashi. This would not only help to keep the sunlight out of the samurai's eyes, but its protrusion would also act as a degree of protection for the face from the extended and downward strike of the enemys sword.

As part of the samurai attire, mainly for those of higher importance an eboshi, a silk cap-like headgear would be worn under the helmet. As the samurai during this early time of the Gempei War fought much on horseback and utilized bows and arrows, the right arm of the standard samurai soldier had no restricting protection to allow for the drawing back of the bow. A light protective sleeve was worn on the left arm.

Not all fighters during the Gempei War were of the samurai class, and therefore were equipped differently and wore a different style of lighter armor called the 'Do Maru'. A body Wrap style of armor resting on the shoulders and fastening under the right armpit was far less restricting than the yoroi. It was based on this freer design of armor that development would be made for the samurai's armor of the future.