The Second Battle of El Alamein during the Second World War led to changes in military tactics and strategies and was a fatal blow to the Nazi Army from which they would never recover, thus altering the course of the war.
"In the situation in which you find yourself there can be no other thought but to stand fast, yield not a yard of ground and throw every gun and every man into the battle...Your enemy, despite his superiority, must also be at the end of his strength. It would not be the first time in history that a strong will has triumphed over the bigger battalions. As to your troops, you can show them no other road than that to victory or death."
-Adolf Hitler to Erwin Rommel, November 3, 1942