Speaking about High Middle Ages classic "knightly" warrior with Longsword.
It seems like "askhually swords can't do anything against armor and knights used maces and warhammers" has recently become every Joe's go-to whenever any medieval topic pops up somewhere in the internet. While I don't deny the role of polearms on every mediaval battlefield, the useless sword theory just doesn't seem right to me.
If swords were so inferior to other weapons, why did they make so many of them? Surviving medieval armories are equally full of breastplates, bascinets, polearms and Longswords. Many say that sword was used for personal protection, which is true for smaller sidearms (later evolving into Rapiers and Sabres), but Longswords are simply too big for day-to-day use.
Others mention that not everyone would be fighting in full plate, so swords could work against lightly armored combatants, but knights in the 1400s were so much into their knightly stuff, that a status weapon existing only to slap around peasants doesn't make much sense (many at that time would probably also consider fighting non-knights as beneath them). Another thing is that a polearm would work equally well against lightly armored opponent, so there would be little reason to carry around two weapons just to have any use for a sword.
So, what would make a person use a Longsword in a mid-1400s battle of two armies packed head to toe in steel? Is it just more versatile and does many things well enough compared to a more specialized tool like a spear or Bec De Corbin? More dependable because of no wooden parts? Weight distribution and balance make it work differently than polearms? Better for grappling? Maybe fighting a knight was much more stab-centric and chances of landing a good haymaker with a polearm much lower that we would think ?
I can speak primarily from the perspective of Eastern Europe, which didn't have as many plate armoured units as Western Europe did, but sword (especially longswords) surely had its usage against armour, preferrably for thrusting between the gaps of armour plates (take a look at this for reference). Hopefully other Redditors can fully answer regarding the Western part. Also it is very important to remember that amount of knights in full plate armour in a single battle usually wasn't very high: they were invauables resources best used sparingly, and it was very possible that amount of heavy cavalrymen to be below 100 men or so [1], thus they sometimes had to use weapons against different kinds of targets, same for their enemies - they often didn't have enough armour-breaking tools so had to use what was available.
which is true for smaller sidearms (later evolving into Rapiers and Sabres)
This is somewhat incorrect. Sabers coexisted with straight straight swords for many centuries, although you probably can say that "typical" Medieval swords indeed later fell out of grace.
but knights in the 1400s were so much into their knightly stuff, that a status weapon existing only to slap around peasants doesn't make much sense
Not everybody who isn't a knight on the battlefield was a peasant. In 15th century a lot of European armies employed big quantities of more lightly armoured mercenaries and men at arms which usually were much more numerous than heavy knight cavalry. Also don't forget Eastern opponents Medieval Europe had to face which usually were more lightly armoured [2].
many at that time would probably also consider fighting non-knights as beneath them
I'd say that beneath or above are not the terms a person has to consider when he's surrounded from all sides knowing that the enemy doesn't want to take prisoners.
Still, it is important to understand that full plate armour was very expensive and very effective before mass produced firearms made it history, there weren't "right" ways to deal with it on a daily basis as these knights were pretty rare and formiddable opponents. Even hammers and axes could be ineffective, but generally they were more preferrable option compared to swords. This also includes Eastern European powers when they had to engage knights in combat, as Bec De Corbin was very popular weapon for mounted combat (example, although it's from 17th century) [2]. So no, swords weren't useless at all, but knights usually carried different weapons with them - for different needs.
