- May 2018
I think that one thing that gunpowder did was significantly reduce the amount of training an effective soldier required.War is a nasty business, a certain level of physical and psychological strength is required for any soldier to be effective and endure the reality of combat. This toughness is usually gained through training and experience, though there are some people that are simply more fit for war than others.
I think that warfare in the past naturally required more physical strength and agility due to the absence of gunpowder weapons and the technological limitations, for one to swing a battleaxe or to wear armour for days on end considerable psychical strength and endurance are needed.
Now, this doesn't mean that modern warfare is clean or doesn't require toughness. Going into a battle and fighting effectively, manoeuvering across the battlefield etc. requires considerable strength and stamina also. In the age of linear warfare when muskets were inaccurate after a certain range and were faulty soldiers required good discipline and skill to aim and fire them effectively, or at least more accurately and faster than their enemies. Also, going into a battle and holding fire while marching in a line certainly required discipline in itself.
This said I think that it's beyond inaccurate to say that toughness disappeared with the spread of gunpowder weapons, at least up to World War I fighting still required discipline, strength and toughness. In the modern age I would say that being a U.S. soldier in Vietnam or a guerilla insurgent in Afghanistan obviously requires toughness skill to survive and be effective.
I also think that there's partially a romantic image involved here: It's far more engaging to imagine Viking warriors fighting in a brutal melee and armies butchering each other by hand or Wellington on a horse leading a charge at Assaye while line infantry fights around him than Alan Brooke sitting in an office in London and directing a campaign in North Africa while the soldiers fight with more modern weapons.
A swordsman, archer, hoplite, legionnaire, and even more so, mounted knight required years of training both in their individual weapon as well as drilling as a team. With the introduction of the musket, I can make a man as deadly as a 6'6 Gallic Barbarian, or rather, a 12 year old girl with a pistol could kill a 6'6 Gallic barbarian, no problem. There really isn't any ancient soldier weapon where this could happen, and that girl could be proficient enough with that pistol to kill a person without much training.
While many ancient soldiers weapons could (and were) wielded effectively by those with little training...sometimes...the fact remains that I can make an infantryman more deadly than a Roman Legionary in under 12 weeks. When Roman Legionaries existed, nobody could take a raw recruit and make them that deadly in 12 weeks.
The flipside, of course, is the fact that we have modern weapons, some of which require years of training just to attain basic proficiency. The current naval aviator program is multiple years long.