When land was held by feudal tenure, military service was due from a tenant to his lord. This normally consisted of the provision of a knight for 40 days from each knight's fee. The practice was widespread in medieval Europe; its use in England has been the subject of detailed study. Evidence from elsewhere is less full, although a detailed survey of feudal obligations, which dates from the 1160s, survives from southern Italy.
The question of whether the system was introduced to England in fully fledged form by William ‘the Conqueror’ has been much disputed. Although there were some similarities with earlier Anglo-Saxon practice, it is difficult to deny that the tenurial revolution which followed the Norman Conquest witnessed the introduction of a new system of military obligation. There is only one surviving writ from the Conqueror's reign requesting military service. The fullest evidence for the system is provided by an inquiry made in 1166, which shows that tenants-in-chief normally owed service in multiples of ten knights. Scutage might be paid in place of performing service; the system was as much fiscal as military. By 1166 there were over 5, 000 knight's fees in England, but it is doubtful whether actual service on that scale was ever obtained. In 1157 Henry II requested one-third of the total service, and two years later took scutage from most of his tenants, rather than asking them to provide knights. In the early 13th century the service quotas were radically reduced in a piecemeal process. In 1245 Peter of Savoy, whose traditional quota stood at 140, was prepared to acknowledge that he owed a mere five knights, although he in fact provided thirteen. Despite these reductions, Edward I and Edward II continued to demand service; the largest feudal force that Edward I obtained, in 1277, consisted of 228 knights and 294 sergeants. The 400 men registered as performing feudal service in 1300 probably amounted to less than a quarter of the total cavalry force. Tradition, and the fact that the tenants-in-chief benefited from taking scutages from their own sub-tenants, explains why feudal summonses continued to be issued. The last effective English feudal summons was issued in 1327; a revival of the practice in 1385 was undertaken for financial, not military, purposes. Henry V revived feudal service in Normandy, where many summonses were issued in the first half of the 15th century.
— Michael Prestwich
