There's much talk about "shock" in military (history) literature. The Soviets even designated entire armies to be "Shock armies". It's widely acknowledged that cavalry had a "shock" role in battle till the 19th century and that armour has taken over this role.
Yet, I've been unable to locate literature on what "shock" really means in a military context. I have thus deduced this unsatisfactory definition based on the observation of the word in use:
Shock is the defence-diminishing psychological effect of an attack with unusually quick effect.
Now there's a relatively recent article by Jim Storr who attempts to define and research the phenomenon a bit better:
‘Shock effect’ is a state where all or part of the enemy is rendered numb, lifeless, inactive or acting irrationally. ‘Shock action’ is the sudden, concentrated application of violence. It has been associated with rapid approach, such as a cavalry or bayonet charge, a tank attack, or a dive bomb attack. More importantly, it also includes the effect of concentrated HE fire.
This is really basic research on the topic. That's astonishing given the widespread use of the term in military writing for about 80 years.
I don't really like his idea because the infantry gun concept is unnecessarily elaborate for indirect fires (in comparison with mortars) and extremely risky for direct fire (in face of enemy indirect fire support). There's furthermore the question whether it's competitive (against portable grenade projection weapons or even an automatic grenade launcher on wheels).
His example scenario includes the pursuit of the enemy by attack helicopters - a form of support that should make infantry guns unnecessary in the first place.
The general idea of irresistible direct HE support fires is valid, of course. It's proved its ability to push defenders out of most defensive positions in many wars. Its limitations in a mountainous/hilly terrain (as in Storr's example) is that direct fire weapons can only defeat forward slope positions, and rarely ridge positions. A competent enemy will prefer reverse slope positions and use the ridge only for observation and rarely for firing.
The real challenge in hill/mountain fighting* is thus out of the field of fire of such direct fire weapons, which can often be substituted for by slower indirect fires.
In the end, I'm much more interested in a theory of shock in the context of conventional ground combat. How could shock tactics contribute to the ability to knock out, overrun and disintegrate an enemy brigade quickly and without incurring huge KIA counts? How does shock help us to turn enemies into prisoners of war?
Shock is an interesting patch of the huge mosaic picture that we call "warfare". We should understand it better than we do, and that would then be the starting point for a cascade of considerations and conclusions that could contribute to better tactics and operational art.
*: I'm preparing a long blog post on this.