Originally, the samurai had started out as mounted archers who carried swords, as opposed to the sword wielding infantry most westerners are familiar with. The mounted warriors wore armor of a paneled skirt hung from the shoulders and fastened at the waist. The armor was made of horizontal rows of lacquered iron or leather, tied together with braided silk chords. They also wore rectangular shoulder guards, and had shin guards to protect their legs. Chain mail protected only the arm that held the bow, leaving the second arm free to draw the bowstring. As the wars moved to more heavily wooded and hilly terrain, the samurai became primarily a foot soldier. The armor of the foot soldier was mostly the same as that of the armored rider, except for a weight reduction, and the the addition of thigh pads, as well as chain mail for both arms. The helmet was made of iron plates with hanging neck guards, a facemask, and a throat guard. Each samurai wore a device known as a sashimono during battle that would separate the two opposing armies, so that a soldier would not kill members of his own side.
The samurai went into battle armed with a bow, dagger, and one to two swords. They also carried a deerskin for sitting on during archery practice that was also used as a seat if they were to be executed. Many higher samurai would blacken their teeth, apply powder and perfume, and tie a topknot before battle, so that if they were killed and beheaded (as was common practice) they could retain their dignity even after death. The standard samurai sword was known as a katana, short swords were called wakizashi, and extra long swords bore the name no-dachi.
Traditionally the samurai would commence an attack by firing an arrow with a whistling head to signal the start of battle. Then one by one they would ride forward to seek out an individual warrior of comparable rank for man to man combat. To find an opponent he would ride around loudly announcing his family lineage and their accomplishments. Once paired against an opponent, he would charge forward on his horse and try to stun or unseat him with his sword, and then kill him with a dagger. After battle a samurai would then take the heads of those he had killed to his overlord as trophies and proof of his kills. This all changed with the coming of the Mongols, who forced the Japanese to develop the use of formations and massive armies. Before this time it was not uncommon for a samurai to strike it out on his own during battle in search of special rewards and greater glory. Afterwards though, "the great generals thought not in terms of samurai, but of samurai armies, where individual prowess was valued in terms of its contribution to a carefully planned strategy."
Soon samurai armies were being largely supplemented by lower class warriors called "ashigaru" which means "light foot." These were fundamentally peasant mercenaries, but near the end of the samurai age they had become the largest and most significant part of a Japanese army. By the late 1500's gunpowder was beginning to dominate the battlefield, and the arquebusier, a foot soldier armed with a primitive musket or "teppo" had become the most important of the ashigaru in the samurai army.