October 25, St. Crispin's Day, marks the high and low in British martial history. I nominate as high the Battle of Agincourt, recounted in Shakespeare's Henry V (did you watch The Hollow Crown?).
As Shakespeare wrote the story, Henry imploring his men to battle, before outlandish odds, is perhaps the most inspirational speech ever given. The English victory impressive, the gains short lived.
The British military does not have a monopoly on stupid, but bad things happen when leaders look upon their fighting men as DNOK, the other. On St. Crispin's Day, four hundred forty odd years after the Battle of Agincourt, the British army was back on the field, this time fighting Russians at Balaclava in the Crimea. Misunderstanding their muddled orders, a sabre armed light cavalry brigade was sent headlong into battle against entrenched Russian artillery. The results predictable.
The BBC tells the story surprisingly well in this video.
Alfred, Lord Tennyson, wrote the best known chronicle of the battle
5 hours ago