From 1340, English kings, beginning with Edward III, claimed to be the rightful kings of France and fought the Hundred Years' War, in part, to enforce their claim. Every English and, later, British monarch from Edward to George III, until 1802, included in their titles king or queen of France. This was despite the English losing the Hundred Years' War by 1453 and failing to secure the crown in several attempted invasions of France over the following seventy years. From the early 16th century, the claim lacked any credible possibility of realisation and faded as a political issue.
Edward's claim was based on his being, through his mother, the nearest male relative of the last direct line Capetian king of France, Charles IV, who died in 1328. However, Philip of Valois, from a cadet branch of the Capetians, became king instead, as the French magnates preferred a French rather than a foreign monarch. The justification was that the crown could not be inherited through the female line and Philip was Charles's nearest male relative through the male line. Edward spent most of the rest of his life at war with Philip and his Valois successors, in part, to pursue his claim to the throne, although Edward's main concern was, in fact, to protect his rights to his lands in Gascony, in south west France. He never succeeded in taking the French crown and after he died in 1377, the war petered out. However, subsequent English monarchs traced their claim to the French throne to Edward.
In 1415, the Lancastrian king, Henry V, revived the claim after a period of peace and invaded France. Following his crushing defeat of the French at Agincourt, he succeeded in taking control of northern France and was declared heir of the Valois king, Charles VI. Both kings died in 1422 and Henry's son, Henry VI, was crowned king of both countries, creating the so-called dual monarchy of England and France. However, French resistance to the dual monarchy resulted in the English being expelled from France by 1453, ending the Hundred Years' War but leaving Calais as the last remaining English possession. Further unsuccessful invasions to claim the throne were attempted by Edward IV in 1475, Henry VII in 1492 and, finally, by Henry VIII who repeatedly invaded France between 1513 and 1523 to secure the crown. By this time the claim had become wholly unrealistic. England and France would continue to fight wars but none were over the claim to the crown. Calais was lost in 1558 but monarchs of England and Great Britain nevertheless continued to include France in their titles, even in treaties with French kings. Because of the improbable and unrealistic nature of the claim, the inclusion was without controversy. However, following the French Revolution, the new republican government of France objected to the practice and the title was abandoned finally in 1802.