By far the most important items owned by the warrior were their personal arms and armor, which provided both protection in battle and a vehicle for personal display. Samurai armor and helmets evolved and improved through time to adapt to changing styles of warfare and to achieve greater efficiency in battle. But apart from their utilitarian functions, suits of armor, helmets, and swords were also objects treasured as symbols of strength, identity, and power. The shogun and daimyo often recognized service and merit by awarding loyal samurai vassals (men bound to their lords by vows of loyalty and/or other contractual obligations) with gifts of armor, helmets, and swords. Suits of armor were used for samurai burials, confiscated as the spoils of war, displayed or worn at ceremonies, and given as votive offerings to Buddhist temples and Shinto shrines.
The oldest surviving representations of Japanese armor and helmets are found among the artifacts excavated from ancient tombs (around 300–500). During this period, clay figurines (haniwa) placed atop burial mounds as part of mortuary rituals included soldiers wearing armor. The design of this early military equipment was based on prototypes from China and Korea. During the 800s, as the warrior class rose to prominence, a distinctively Japanese style of armor, the oyoroi (lit. “great armor”) developed. Armor-makers designed this boxy style of protective gear to be worn by high-ranking warriors, who rode on horseback and used the bow and arrow and sword as weapons. The stiff and heavy body was built up of small rectangular iron or leather plates (lames), laced together with brilliantly colored silk cords or leather to form beautiful patterns. A divided, armored skirt, suspended from the body, armored sleeves, and shoulder, thigh, and shin guards complete the protective equipment. Helmets from this period are low bowls made from metal plates riveted together, with a hole on top for the wearer’s hair to pass through. A guard for the back and sides of the head, constructed from rows of laced plates, hangs from the base of most samurai helmets.
Foot soldiers and attendants used a spear as their main weapon, and wore lighter armor (domaru) constructed with a continuous, sheath-like torso. As fighting on foot and long campaigns became the norm during the 1300s, the more flexible, lighter armor was adopted by higher-ranking samurai as well. With this was worn a large, high-sided helmet lined with cloth or leather to absorb shock.
The introduction of firearms from the West after 1543 forced armor-makers to innovate. Use of guns made it necessary to develop a new type of armor, capable of sustaining the impact of musket fire. To meet this demand, armor makers experimented with different combinations of overlaping and welding larger and stronger metal pieces for protection. Lacing, which required piercing and thus weakened the metal, was partially displaced by rivets and hinges. This new type of armor, known as tosei gusoku (lit. “modern armor”), had many possible variations in style, including the use of a hinged metal breastplate reminiscent of a European cuirass (protective shell that includes a breastplate and backplate). In the same period, the helmets of high-ranking samurai were often embellished with magnificent ornaments. These distinctive devices helped the warrior to stand out among tens of thousands of enemies and allies, ensuring that his actions were visible to all.