When Henry V became king of England in 1413 he inherited an exhausted realm. The coup d'etat in which Henry's father deposed his uncle Richard II had left deep political fault-lines; the impact of the Black Death still lingered; public finances and law and order were in crisis. To the outside world, England was irrelevant, the glorious victories over France won by Henry's grandfather Edward III at Cre¿cy and Poitiers largely forgotten.

But, in less than a decade, Henry transformed England. He reunited the political community behind the crown, reformed the justice system, invested heavily in shipbuilding, put down rebellions and secured England's borders. In foreign diplomacy, he made England a serious player once more. And, by defeating a larger and better-equipped French army at the battle of Agincourt in 1415, he brought about the union of the crowns of England and France, an achievement which ranks Henry alongside medieval rulers such as Charlemagne, William the Conqueror and Frederick Hohenstaufen.

In terms of his military genius and force of personality, Henry was arguably the closest thing England ever produced to a Napoleon Bonaparte. And Agincourt was his Austerlitz.

Dan Jones is the Sunday Times and New York Times bestselling author of many non-fiction books, including The Plantagenets, The Templars and Powers and Thrones. He is a renowned writer, broadcaster and journalist. He has presented dozens of TV shows, including the Netflix series Secrets of Great British Castles, and writes and hosts the podcast This is History. His debut novel, Essex Dogs, is the first in a series following the fortunes of ordinary soldiers in the early years of the Hundred Years' War. He is a Fellow of the Royal Historical Society.