The usurpation of 1399 provided a precedent and a model which exercised a profound influence over the politics and government of fifteenth-century England. The dubious title of the Lancastrians diluted the hereditary principle and thus widened the field of potential claimants to the crown. The Lancastrian era, from Henry IV's usurpation until Henry VI's deposition in 1461, was dominated by three interwoven themes: warfare, service and finance. Henry V's elder surviving brother. The crisis of the Lancastrian monarchy was inevitably precipitated by events in France. The cohesion amongst the leading magnates, long sustained by the common purpose of defending Lancastrian France, began to disintegrate. In May loyal Lancastrians were summoned to Leicester for military service, and the following month a great council was held at Coventry. The victories of Henry V, culminating in the Treaty of Troyes, linked the fortunes of the Lancastrian dynasty inextricably to continued military success in France.