It seems that as plate armour develops in Europe we see a very direct response in weapon design. Weapons like poleaxes and rondell daggers appear, sword design becomes much more thrusting-oriented and percussive weapons like maces and warhammers become much more prolific than they were in the age of mail.

I find this confusing. Cutting-oriented swords are among the least effective weapons to use against mail and yet swords with rigid cross sections only seem to develop when mail armour starts to get augmented with early forms of plate. Maces and warhammers aren't nearly as common in the age of mail as they become in the age of plate. Poleaxes too seem like they would be greatly effective against mail yet as far as I can tell they only come about to counter plate armour.

So to sum up, weapons that are optimized to oppose metal armour don't seem to proliferate until the rise of plate armour and yet in the age of mail there should still be plently of need for percussive weapons and rigid swords.

Axes, spears, mounting the spearman on a horse and using the horse's momentum (i.e. development of lances), all increased the power over that available from the sword (which was primarily a side-arm).
Until the age of plate (i.e. whilst mail was the top of the line protection), most people on the battle-field would lack substantial metal armour. Swords of the period were perfectly adequate for cutting unarmoured targets (which most would have been) and the elite who were armoured used axe and lance (and mace) on each other.

As I understand it, plate armor developed in direct response to increased infrastructure for making iron plate. There were developments in smelting and in forging, and towns that saw a number of shops setting up to create armor production centers. The mail-makers were not left behind, they were able to ramp up production as well.

More armor available to men of less wealth meant they could more easily (safely!) dispense with shields and use 2-handed weapons. Such weapons are simply more effective overall, but it seems to me that the general rule was still to aim at UNarmored spots, if at all possible. Deliberately trying to penetrate any kind of armor was risky.

Matthew

Matt Easton's take on this exact subject:

https://www.youtube.com/watch?v=gVrYt5A3VyA