When learning about Ancient Rome, it’s common to hear that the Hoplite, a soldier with a spear and shield, was the best type of warrior one could ask for.
But centuries later, we see knights using swords (and maces and axes and whatnot). I have a hard time understanding why hoplites disappeared, when they’d clearly have the reach advantage against a knight with a sword.
And centuries after that, during colonial Britain times, we see rapiers and the fencing style of combat emerge. Most depictions of those with rapiers don’t show the wielded having much armor either (at least not compared to a knight). Again, I’d have a hard time seeing that combat style winning against a knight or hoplite.
So why did Europe switch from spear/shield, to swords and heavy knight armor, then to rapiers and light/no armor?
As for your primary question, I found these answers from /u/Iphikrates and /u/Agrippa911 to be informative on the subject.
But in response to one particular part of your question:
And centuries after that, during colonial Britain times, we see rapiers and the fencing style of combat emerge. Most depictions of those with rapiers don’t show the wielded having much armor either (at least not compared to a knight). Again, I’d have a hard time seeing that combat style winning against a knight or hoplite.
The answer there is simple: the rapier is not a weapon of war. Rapiers were for civilians to use for self defense or to duel each other with, not for soldiers to use on the battlefield.