Gunyaku (also known as Guneki) was a military service and provisions that was imposed by the lord on a retainer to offer in wartime.
In a broad sense, gunyaku meant conscription which included the labor service that was imposed on the people; but in a narrow sense, gunyaku referred to a retainer's offering of military service to the lord in exchange for recognition and guarantee of ownership of the fief (debt) in the relationship of 'debts and service' in the feudal system.
Sway over lands in the middle ages had not been evolved to 'one lord in one land' as in the Early-Modern period yet, and the swaying system was much more complicated than that of the Early-Modern ages. There was a multilayered structure of rights claimed for a land including 'saku-shiki' which meant the right of cultivation, 'myoshu' which referred to the right to collect land taxes, and 'jito-shiki' which was responsible for paying out land taxes to the lord of the manor; besides, as the provincial government office and the military governor possessed influence on each province, master-servant relationships among samurai were not necessarily a simple one-to-one relationship. After a while, samurai began encroaching the manors and gradually established contrrol over the manors by paying an influential higher ranking samurai, who was able to warrant the samurai the control over the land, in a military service instead of land tax.
During the Heian period, the lord of the manor called 'ryoke' or 'honjo' legally warranted samurai the control over the manor; on the other hand, the local notables who actually developed the land did office-seeking by assiduously contributing their territory, offering a certificate given to the leader with the retainer's name on it and had his sons be retainers. In the meantime, the local nobles who developed the land, as a resident of the province, was made to offer military service by the district government office and presented himself for duty as the local officials. The oldest style of military service imposed on samurai was supposed to have been military service when samurai served the lord of the manor as a retainer or presented himself for duty at the provincial government office.
Later, the higher ranking samurai families such as the Minamoto clan or the Taira family, which had relationships with persons of noble birth were entrusted to warrant the local nobles their developed lands, and a system was established in which middle and lower ranking samurai were called 'kyunin' who offered military services to the lord not only in peacetime but also in wartime in exchange for the land which the lord granted them as stipend. Since there was a multilayered structure of influence put on a land as mentioned above, the resident landholder sometimes asked not only the shogunate but also influential court nobles, the governor of a province or the military governor, or resident influential samurai family for recognition and gurantee of the ownership of the land, for the purpose of protecting the ownership of his land.
The military service imposed on the immediate vassals of the shogunate in the Kamakura period included the guard duty in Kyoto and Kamakura, to search and capture and the like, and in wartime, they would summarily rush to the place, 'Iza Kamakura' (To Kamakura with haste). The military services were based neither on the area nor crop yields of of territories, and the military force to mobilize was left to the discretion of each of the immediate vassals of the shogunate. Since the territory was not increased as much as excessive military services imposed during the Mongolian Expeditions against Japan, dissatisfaction built up among the samurai retainers with the the head of the Hojo clan regent of the Kamakura bakufu (Japanese feudal government headed by a shogun), which supposedly formed a remote cause of the fall of the Kamakura bakufu.
In the period of the Northern and Southern Courts (Japan), small and medium samurai warrior band in provinces asked not only the new head of the government, the Genji-descent Ashikaga clan, but also the territorial lord as provincial constable, which had increased its influence after the order allowing military governors or Shugo to collect half of the taxes from manors and demesnes as military fund was issued, and influential samurai families on the side of the Southern Court or the Northern Court for recognition and gurantee of the ownership of their lands. The Muromachi bakufu formed the military guard of the shogunate from branch families of the territorial lords as provincial constable and hereditary vassals of Ashikaga clan and imposed service in Kyoto on them; on the other hand, the territorial lords as provincial constable tightened control over the local lords in their provinces and imposed military services on them according to their territories. As the military strategy changed from the one-to-one duels by horsemen to the party and army battle, the military service had been based on the area and the crop yields of the territory.
The military service was also imposed on local clans and local samurai, both of which lived partly on farming and partly on a samurai warrior stipend. According to the example of the estate of Erin-ji Temple, the Takeda family's ancestral temple, in addition to the smallest unit of the lowest position of vassals devoted themselves to military arts, there were a band of farmers exempt from a part of their land taxes. Unlike common landholders, they contributed military services to the Takeda family in wartime in exchange for being exempt from part of their land taxes and labor services. Similar systems were found in each of the domains of the territorial lords during the Warring States period, during the age when the warriors and the peasants were unseparated; the band of farmers contributed to the military forces of each of the territorial lords' families until the cadastral surveys instituted by Hideyoshi TOYOTOMI was enforced and warriors and peasants were separated. The basis for the military service imposed on the vessels in the terrritorial lords's families was changed from the money taxation system to the food taxation system in the Early-Modern period, which is another characteristic of gunyaku system.
The military services imposed on the middle and lower ranking samurai who offered military services to the lord by lords such as the territorial lords were defined by 'the number of Mounted Warriors, the number of Bows, the number of Muskets, the number of Spears, and the number of Banners,' to which manpower including the numbers of such laborers as caravan of men and animals carrying supplies and low ranked people was sometimes additionally defined. In the Azuchi-Momoyama period, the military service defined by the Toyotomi clan such as '250 men per 1,000,000 koku' may have been made up like that shown above.
Military service in the early Edo period
The military service was not based on a certain standard and imposed for each occasion during the Kamakura and the Muromachi periods; and the Edo shogunate standardized that. In 1615, upon fighting the Summer Battle of Osaka, Hidetada TOKUGAWA issued the military order to appoint armies to their posts and to define the military service and imposed them on the army. The system at that time is shown below.
500 koku - one Musket, three Spears including spear owned by Mounted Warrior
1000 koku - two Muskets, one Bow, five Spears including spears owned by Mounted Warriors, one Mounted Warrior
2000 koku - three Muskets, two Bows, ten Spears including spears owned by mounted warriors, three mounted Warriors
3000 koku - five Muskets, three Bows, fifteen Spears including spears owned by Mounted Warriors, four Mounted Warriors (one Banner)
4000 koku - six Muskets, four Bows, twenty Spears including spears owned by mounted warriors, six Mounted Warriors (two Banners)
5000 koku - ten Muskets, five Bows, twenty-five Spears including spears owned by mounted warriors, seven Mounted Warriors (two Banners)
10000 koku - twenty Muskets, ten Bows, fifty Spears including spears owned by mounted warriors, fourteen Mounted Warriors (Banners)
The system after the Revision in June 1616 is as below.
500 koku - one Muskets, and three Spears including spear owned by horse soldier
1000 koku - two Muskets, five Spears including spears owned by horse soldiers, one Bow, one Horse Soldier
2000 koku - three Muskets, five (or fifteen?) Spears including spears owned by horse soldies, two Bows, three Horse Soldiers
3000 koku - five Muskets, fifteen Spears including spears owned by horse soldies, three Bows, four Horse Soldiers, one Banner
4000 koku - six Muskets, twenty Spears including spears owned by horse soldies, four Bows, six Horse Soldiers, one Banner
5000 koku - ten Muskets, twenty-five Spears including spears owned by horse soldies, ten Bows, fourteen Horse Soldiers, three Banners
10000 koku - twenty Muskets, fifty Spears including spears owned by horse soldies, ten Bows, fourteen Horse Soldiers, three Banners