Are snipers and recon still valid in infantry battalions?

[William F. Owen]

Average and median are really of little interest.

A WW2 armoured corps with 40 km/h tanks* advanced 400 km in quite exactly four days- against the opposition of several conventional divisions in suboptimal tank terrain (Manstein's Corps to Vilnius)

So that figure is a sound basis for discussion, based on the fact it happened once?

Advance through defence is of little interest today in general. There are enough gaps for advance, and no continuous line of defence. You don't need to advance through deep defensive positions in most conventional warfare scenarios.

On what do you base that assertion. You are stating a fact?
How do you know where the enemy defence is? Finding the defence is the problem we are discussing.

You can - if you prepare well for it - rather go back to an extremely accelerated version of Central European 18th century army maneuvers (Wars of Silesia as examples).
Speed of advanced in defended terrain was irrelevant then and it is (almost) today.

So how do we do this? What do you suggest as useful data sets around which to base a discussion?