Agincourt should not only be one of England's greatest victories, but one of the greatest battles in military history. It is one of several battles throughout history where a outnumbered and arguably outclassed army was victorious due to a leader's careful use of terrain. Henry V was able to overcome great numerical odds by using the upslopping and muddy terrain to slow the French advance. This allowed him to maximize the use of his archers, which historians agree was critical to his victory.
More intangibly, the fact that he denied ransom from the French army should he or his nobles be captured, showed great solidarity with his men, thus the "band of brothers" ethos. By dismounting and fighting on-foot at the center of his formation, arguably inspired his archers to do the same, when English archers were reluctant to fight hand-to-hand in the past. Although history sometimes refers to this as "the day chivalry died" I think it was the birth of a new form of chivalry that is held among fighting men. This moment in history showed that all men are important in combat, not just the nobles, and that all Soldiers can influence the tide of battle. This concept continues today and is known as the "tactical corporal" phenomenon.
I personally think that The English mowed down the French knights with just a lightly armed force fighting with the welsh longbow. As indeed had the English on many earlier occasions in the 'hundred years war'. Agincourt has however become one of our defining English legends while Curacy and Poitiers have not. However what is victory, we won the battle but not the war. Indeed there are numerous other possible battles with the British as the winner, Clive's victory at Plassey for example.
I believe Agincourt is one of the greatest British victories in history. The battle was from the Hundreds Year War and signaled a turning point for the British. The royal families were intertwined through marriage, between France and Britain, following this battle. The British won, despite the French having a better equipped and trained army.
Agincourt placed the British army numerically disadvantaged. It was at Agincourt where the development of the Longbow really was proven. The strategic placement of the slant sticks crippled the use of Cavalry to overrun the Archers. The tactics used at Agincourt proved that projectiles would soon be the staple of every battle, well before guns had been invented. The idea that a battle must be fought hand to hand was no longer popular. This new way of fighting that led to the victory at Agincourt would help Britain 'win' the hundred year war.
Yes, Agincourt was the greatest British victory in history, because it was that victory that secured the British win in the 100 years war. In Agincourt, the British troops were outnumbered by the French. The fighting was hand-to-hand combat. By all accounts, they should not have won. But the British pulled through for the unlikely victory.
No, this was one of the good victories that they had, but I do not think that it was the best that they have ever seen while they have been a country, since they have been a country for a very long time, and have done a whole lot of things.