Songfacts®:

• Also known as the "Agincourt Hymn" or "Agincourt Song," this song in 3/4 time was written in Olde Englishe, and celebrates the victory of Henry V over the French at the Battle of Agincourt which took place on October 25, 1415. As the historian David Starkey pointed out in his 2013 BBC Television documentary series Music And Monarchy, at that time, carols were not specifically and only Christmas songs but were written to celebrate secular events, including military ones.
  
  When Henry turned up at the French port of Harfleur he took not simply his army but an entire choir with him. His victory at Agincourt is legendary because his smaller army of English and Welshmen cut down the superior force with their longbows.
• Although the authorship of the "Agincourt Carol" is not known, it was almost certainly commissioned by Henry V himself shortly after his historic victory. The main indicators of this are the wealth of accurate detail and its clearly heroic portrayal of the monarch. >>>

  Suggestion credit:
  Alexander Baron - London, England, for above 2