Their root is believed to be that of shimobe (下部), who served by the side of government officials during Heian period. Ashigaru (literally "light-foot", but the word most likely stems from "light armored") were the lowest-class warriors, either the low-class buke (warrior class) or commoners who had joined or been impressed to the daimyo's army.
At first the ashigaru were mercenaries or adventurers who were paid only in loot, but eventually some of them became part of local armies as retained warriors. Those who were given control of ashigaru were called ashigarugashira (足軽頭), (literally "ashigaru head"), and were provided with an annual stipend of 200 to 500 koku.
The ashigaru were foot soldiers—the cavalry was the territory of the samurai. They might have been armed with naginata, katana or just with spears (yari) unless they served as handlers of catapults. In the 1500s, they were also armed with arquebuses. As battles became more complex and forces larger, ashigaru were rigorously trained so that they would hold their ranks in the face of enemy fire. Their armour consisted of conical hats (jingasa) made of lacquered hardened leather, breastplates and occasionally greaves protecting the legs. Some also donned small banners on their back during battle for identification purposes, called sashimono. They needed to bring provisions for themselves until reaching local gathering points and from this point on, were provided provisions from the daimyo's warehouses.
In the Ōnin War, ashigaru gained a reputation as unruly troops when they looted and burned Miyako (modern-day Kyoto). In the following Sengoku period the aspect of the battle changed from samurai's man-to-man fight to ashigaru's group combat. Therefore, ashigaru became the main force of battles and some of them rose to greater prominence. The most famous of them was Toyotomi Hideyoshi, who also raised many of his warrior followers to samurai status. Yamauchi Katsutoyo was one of such samurai and later daimyo who rose from ashigaru.
Ashigaru formed the backbone of samurai armies in the later periods. The real change for the ashigaru began in mid 16th century with the introduction of guns from foreign traders, such as the Portuguese. Almost immediately local daimyo started to equip their ashigaru with the new weapon that required little training to use proficiently, as compared to the Japanese longbow which took many years to learn.
The advantage of the new powerful ranged weapon proved decisive to samurai warfare. This was demonstrated at the Battle of Nagashino in 1575, where carefully positioned ashigaru with muskets thwarted Takeda's repeated heavy cavalry charges against the Oda clan's defensive lines and broke the back of the Takeda war machine.
After the battle, the ashigarus' role in the armies were cemented as a very powerful complement to the samurai. The advantage was used in the two invasions of Korea in 1592 and 1597 against the Koreans and later the Chinese. Though the ratio of the guns (muskets) and the bows was 2:1 at the first invasion the ratio became 4:1 at the second invasion since the guns were very effective .
Following the rise of the Tokugawa Shogunate the conscription of ashigaru fell into disuse. Since ashigaru's change to the professional soldier was advanced after Oda Nobunaga, the ashigaru separated from the farmer gradually. When entering Edo period, the ashigaru's position as the lower class samurai was fixed and the use of conscripts was abandoned for over two hundred years in Japan.
Ashigaru is a type of Japanese soldier that began during the Heian Period (794-1185). Their origin is serving as bodyguards to government officials during this period. They became more active over hundreds of years and ended up serving as foot-soldiers for samurai and shogun. Ashigaru became masterless warriors after the beginning of the Edo Period (1603-1868). After the Edo Period, many became police.
Ashigaru are noted for using surprise attacks and group tactics. They wore metal armor, a gauntlet, and a Japanese half-length coat. The armor also had leather and Japanese rice paper. Their weapon was a sword, spear, gun, or bow. Ashigaru also carried a water bottle, tissue paper, and rice.
In the Onin Rebellion (1467-1477), the ashigaru robbed and looted Kyoto. This gave ashigaru a reputation as bad troops.