G.a. Henty 
At Agincourt [EPUB ebook] 

The story of Guy Aylmer, a young 17 year old esquire and man-at-arms, whose leige lord, Sir Eustace, is a knight with castles and allegiances in both England and France during the Hundred Years' War. Guy's father is castelain over Sir Eustace's lands in England when Sir Eustace is away in France. Guy is second-in-command over a contingent of 30 men-at-arms and 25 English longbowmen serving in defense of Sir Eustace's castle in France during the disturbances following the Duke of Burguny's murder of the Duke of Orleans, the brother of the sometimes-mad King Charles II of France…