Battle of Hastings 1066 (Changed England & Europe),
Battle of Agincourt 1415 (End of Chivalry),
Harpers Ferry (Alerted the South to Arm themselves)
Unless you were a Southerner who wished to remain in the Union. The right to bear arms for those people did not mean much in the eyes of the Confederate bosses.
The charge of the Light Brigade also on the 25th