(First a disclaimer: I'm going to write about warfare with opponents who have corrected vision, comparable combat morale and who can aim.)
Some authors claim that a German infantry squad of WW2 typically had 80% of its firepower concentrated in its one machine gun; a MG34 or MG42.
That was probably quite correct, but the carried ammunition and practical rate of fire indicate a slight exaggeration.
The issue was more fundamental than simple mechanical or material statistics, though. A machine gunner has the feeling that he can actually achieve much in battle and has typically a different psychology in effect than most other soldiers have.
Infantry is not all the same - you cannot give a special weapon to just anyone and expect always the same results. Differences are also deeper than mere qualifications and physical fitness or strength.
Some soldiers are aggressive, many are capable if lead well and some are basically porters, not fighters. The most basic problem for infantry is therefore to identify who belongs to which group and to assign jobs and missions accordingly (and possibly reject the porter guys).
The aggressive, daring guys who are very difficult to suppress need to become leaders (the smart ones) or operators for the most important weapons (such as a machine gun).
A 80/20 or 70/30 rule of thumb fits to many forms of human activity: 20-30% of the people have 80-70% of the overall effect (Pareto Principle). This is applicable to the spreading of diseases, the work in staffs, the kills of World War fighter pilots, the number of friends on social networking sites, the performance of snipers, the performance of computer gamers, the success in flirting and it's also relevant for infantry combat.
We can dream on in fantasy land and look at a platoon as a small unit of 20-50 equal men, but that's not going to be confirmed in intense combat.
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OK, let's say we succeed to assign the most valuable men to the leadership jobs or give them the most powerful weapons. What does this tell us about the others in the platoon or squad?
The readers may not like it, but to be honest; the average assault rifle user will be little more than an ammunition porter for the main weapons and a rear/flank security man and message relay.
How does this fit to the everyone-a-super-soldier approach of modern Western infantry equipment programs? The average assault rifle user has got some heavy AT weapon, a designated marksman rifle or an underbarrel grenade launcher nowadays. He's so overloaded with his own kit that carrying additional ammunition for a machine gunner or a platoon commando mortar reduces the mobility to that of a four-year old.
The technology-driven approach with a flair of combined arms (accurate single shots, full auto suppressive fires, high trajectory HE projection) down to squad or even fire team level may be a terrible misunderstanding.
To equip everyone with better rifle optics than were available to WW2 snipers isn't going to turn everyone into a super soldier either. The sights may be worth their weight and bulk, but they don't turn cowards or extremely frightened and shaking men into cold-blooded fighters with an overwhelming lethality in a 400 m radius.
Such equipment will still have the greatest effect with the few men who are psychologically best prepared for combat (this may include being simply too dumb or crazy to understand the danger - in fact, smart people rarely turn out to be among the most daring).
It's probably about time that the psychological differences between infantrymen again consciously influence the setup of infantry small units. This ranges from personnel selection over equipment to tactics and TO&Es (tables of organisation and equipment).
Combat in complex, though. It may be a good idea to 'waste' some good weapons on not very good soldiers in order to distract hostiles, to relieve the few over-performers off (suppressive fires) pressure.
Next, we should keep in mind another pressing challenge: The extreme lethality of modern weapons. Forget about the experiences against unskilled paramilitary (or lesser) fighters in recent warfare. The extreme lethality of modern infantry battalion arsenals (up to 120 mm mortars) restricts the infantry small unit repertoire for most actions. Only very high pay-off actions justify very risky tactics. Most often infantry needs to be very cautious in order to preserve itself for important actions (the military view) and a life after the war (the individual's view).
The combination of high lethality and cautious behaviour leads quite naturally to very short yet intense fire fights with (whenever possible) the advantage of surprise, followed by a quick withdrawal and rallying. The latter is necessary in order to avoid being stuck (and fixed) in a protracted fire fight till hostile mortars end it.
This justifies an emphasis on the right weapons (and munitions) for such an action. A salvo of M72 or SARPAC-like weapons, a very high rate of fire for the machine gun (with an appropriate, stable tripod) and the use of command-detonated mines (~Claymores) are possible answers.
Another approach might emphasize stealth and the avoidance of breaking said stealth. A minimised muzzle fire thanks to suppressors and optimised flash hiders, barrel lengths and cartridges as well as the employment of deception tools (fake muzzle fires) are imaginable.
There's also the possibility that both the own and the hostile infantry are very cautious and often stumble into each other at short range. That could be avoided with detached scout pairs and the use of military dogs, but it's still a possibility. Devastating and immediate fires would be important in this case. Hand grenades might become more important in such situations than all electronics combined and independent (re)actions of all soldiers without much leadership would become most important.
Other patterns for dominant forms of infantry combat are imaginable and need to be considered. Every such form might lead to distinct preferences that could shape the ideal infantry small unit TO&E.
Another hugely important factor in 'real', wars of necessity (if not even total wars) is attrition.
Life expectancy drops to very, very sad levels once a man becomes an infantry lieutenant in wartime. It doesn't look substantially better for infantry NCOs.
A serious army needs to be prepared for appalling losses among its leadership. One way to prepare is to have more leaders than necessary (the U.S. way), another one is to overqualify their subordinates (the old German way).
As far as I can tell, the latter is superior because it enables a very quick adaption once losses happen. A decapitated platoon can continue its mission if an NCO takes the lead, while it would need to wait a while till a replacement leader arrives (and that guy would be unknown to the soldiers).
Some of the most effective and consequential small unit actions in military history have been completed by subordinates who took over command after the initial leaders fell.
This is quite a challenge for TO&Es, for you need enough well-suited men for leading, for employment of the main weapons AND as 2nd or 3rd in command. You don't want to rely on your best machine gunner as emergency platoon leader - that would equal a terrible loss of firepower. The 2nd in command should on the one hand not be too close to the 1st in command, but on the other hand you don't want him too far away. For example, he shouldn't be in the assault element if your army's tactic prefers the platoon leader to be with the fire support element.
Psychological capability in combat, the expected nature of infantry combat and attrition should influence our infantry small unit concepts much more than they seemingly did after the Cold War. Gadget-driven concepts of infantry combat and infantry small unit TO&Es have dominated for about 15 years and are still in fashion. This exaggeration needs to be corrected.
Again, it was impossible to cover the topic comprehensively. I limited myself to mention a few rather rarely discussed aspects of infantry small units setups. Maybe I ruined all the future fun of discussing gun calibres and 40mm underbarrel grenade weapons for you, but that's within the limits of the usual risks of reading this blog...