Henry V, William Shakespeare has the king give his men one of the best speeches ever the night before the Battle of Agincourt. The battle took place on Oct 25th, which is the Feast of St. Crispin. The speech therefore, is known as the St. Crispin's Day Speech.
You'll recognize parts of it. It is from this speech we get the phrase "... we few, we happy few, we band of brothers"