Ashigaru (common foot soldiers) were a type of low-ranking soldier.
Heian, Kamakura and Muromachi periods
The status of ashigaru is thought to have originated during the Heian period from the shimobe (miscellaneous servants and attendants) who served kebiishi (police and judicial chiefs) in the capacity of performing miscellaneous duties and acting as reserve soldiers. Until the mid-Kamakura period, the general practice of one-to-one combat between mounted warriors meant that it was often the case that ashigaru were engaged as servants and porters in fields such as logistics and construction.
As the activity of villains increased and the trend of vassals revolting against their lords became more commonplace during the period of Northern and Southern Courts (Japan), the traditional way in which warfare was conducted began to make the transition from a one-to-one combat to a group battle strategy, and the utilization of ashigaru even spread to the suppression of local and provincial uprisings. During the Onin War, ashigaru groups were used in surprise attacks but their lack of loyalty and their disorder meant that they frequently formed unruly mobs, and there was an incident in which they ran riot and looted Kyoto with its numerous shrines, temples and shops.
Sengoku period (period of warring states)
Ashigaru had not yet been utilized as the main element of battle forces but as they became more well organized and increased in number during the Sengoku period (Japan), they were given training and ashigaru units bearing spears, bows (weapons) and guns were created, going on to form the backbones of armies. In the latter part of the Sengoku period, the intermediate samurai rank of ashigaru taisho (samurai in command of a troop ashigaru) came to be recognized and was awarded an annual stipend of between 200 and 500 koku. The low status held by ashigaru was intermediate between that of samurai and peasants but there were those such as Hideyoshi TOYOTOMI whose abilities were recognized and who rose to the rank of daimyo (feudal lord), although it was a peculiar case.
Group battles fought by large groups of infantry emerged during the Sengoku period and the equipment used by ashigaru followed this trend.
Ashigaru generally wore a conical hat (jingasa) made from lacquer hardened leather or Japanese paper (this was later developed into jingasa made from iron plates that were cut and fashioned into a cone shape), iron body armor, gauntlets and a jinbaori (sleeveless campaign jacket worn over armor) in addition to carrying a canteen, tissue paper, rice wrapped in cloth and other items (e.g. dried taro stems). Rare examples of body armor made from Japanese paper or leather can be seen but the majority of the surviving pieces are made from iron and weigh approximately four kilograms.
Ashigaru units were divided into yarigumi-ashigaru (carrying spears), yumi-ashigaru (carrying bows and arrows), and teppo-ashigaru (carrying firearms), with multiple groups forming units led by a kogashira (a head of small ashigaru group).
Information about aspects such as the lifestyles, drill manuals and the hints of ashigaru of the time is known from "Zohyo Monogatari" (Stories of Common Soldiers). Sengoku period ashigaru were extremely heavily-armored and, with the exception of a large shield, their kit was comparable to that of heavy infantry (however, some ashigaru later went on to wear a haori [a Japanese half-coat] instead to body armor).
As the era of warfare came to a close, the majority of temporarily employed ashigaru were released and became buke hokonin (servant for a samurai family) or ronin (masterless samurai), while the remaining ashigaru served as low ranking members of samurai society.
The Edo bakufu (Japanese feudal government headed by a shogun) employed the ashigaru under its direct control in administrative and policing roles as kachi (foot guards) and doshin (police constables).
The ashigaru under the direct control of daimyo within the various domains were organized into units and during peacetime were used as low-level clerks known as 'monokaki-ashigaru' who served as watchmen and carried out miscellaneous duties. In addition, ashigaru also served as retainers for high-ranking samurai.
The status of ashigaru was restricted to a single generation but in actuality could be inherited by a child or relative upon retirement and, this right later went on to be bought and sold as 'kabu' and also became a position of employment for the second and third sons of wealthy farmers and merchants, because they could make their living by being an ashigaru although their salaries were low.
In addition, the status also had the aspect of serving as a career stepping stone such as when capable individuals who were appointed from among ordinary citizens were temporarily be enrolled with the domain as ashigaru before their subsequent promotion, and what were once gangs of villains during the middle ages took on the identity of low-level public servants.
Ashigaru were also allowed to return to farming and granted the right to bear a surname and to wear a sword as goshi (country samurai) of keikaku (noncommissioned officers) who served as provincial border and frontier guardsmen. An example of this was the 'Jizutsu Korizutsu' firearm unit of Kumamoto Domain, which was essentially an unpaid honorary position. In reality, "firearm unit" was merely a name, and the group was mobilized as locally-hired officers and low-ranking samurai from a domains working in Edo. Conversely, curious children of goshi would also use these systems in order to broaden their horizons by volunteering to serve as domain ashigaru who were dispatched to work in Edo.
During the Edo period there were also ashigaru who served to command chugen (a rank below common soldier) and komono (a lower servant). As Engyo MITAMURA, regarded as 'the father of Edo Studies,' demonstrated in stating 'Ashigaru were soldiers who were approximately equal in status to the noncommissioned officer or private first-class ranks of today; they also conducted the duties of a sergeant,' there were also examples of ashigaru who came to be considered quasi samurai but there are also many cases in which they served as buke hokonin and were regarded in the same light as chugen and komono. Many of the bugencho (registers of vassals) of the domains of Japan do not record the names and stipends of ashigaru and chugen but simply record the number. Some do not even record this. There were also domains in which ashigaru were not differentiated from chugen, were not permitted to bear a surname and were treated as equal to peasants and townspeople. In the Choshu Domain, ashigaru who committed capital crimes were not permitted to commit seppuku (ritual suicide by disembowelment) but were ordained to be crucified, so they were even differentiated from samurai with regard to criminal punishment.
End of Edo period and the Meiji period
At the end of the Edo period, the Edo bakufu and the domains abolished the 'firearm units' which bore matchlock guns and there was a growing need to form western-style infantry units and musket units, but due to the fact that the preexisting ashigaru units had already been disbanded and had virtually disappeared, with those remaining serving as low-level officials and security police, new personnel was recruited and infantry units resembling the ashigaru units of the Sengoku period were created. However, these soldiers were treated as even lower as the chugen and komono which ranked below ashigaru.
The arrival of the Meiji period and system reforms such as Haihan-chiken (the abolition of feudal domains and establishment of prefectures) meant that some doshin and ashigaru continued to serve as police officers, soldiers, noncommissioned officers and low-level officials. Members of the former samurai class were later classified as 'shizoku' (samurai class) and former ashigaru as 'sotsuzoku' (low-ranking samurai). After the subsequent abolition of sotsuzoku, high-ranking members of sotsuzoku were recorded in their family register as 'shizoku' while others were recorded as 'heimin' (commoner) in the same manner as farmers, artisans, and merchants - a system which continued until 1948.
From the middle ages to the end of the early modern era, the recruitment of ordinary people was limited to the support roles of kohei (military engineering) and heitan (military logistics) and such individuals were only mobilized for battle in emergency situations. Ashigaru were conscripted from diverse levels of society as combat troops from the Sengoku period to the Edo period, and there were various employment terms which ranged from temporary employment during wartime to continued employment during peacetime.
These various forms of recruitment mean that ashigaru should also be considered mercenaries. However, as stated above, there were ashigaru who were employed full-time and would serve the same master for several generations, and there were also ashigaru who were treated as samurai, so it can be said that ashigaru occupied a status intermediate between those of mercenaries and feudal soldiers.