just what did a recruit learn at the depot (manual of arms and marching and...)?
Much of it is in the national drill, such as Britain's "Rules and Regulations", or France's "Réglement concernant l'exercice de l'infanterie du 1er août 1791". There are similar major parts, such as, in the latter: "Ecole de Soldat" (School of the Soldier), "Ecole de Peloton" (School of the Company), "Ecole de Battailon" (School of the Battalion), among others, which are typically found in most national drill regulations for a couple hundred years. It is a progressive teaching system, focusing first on the individual, then small groups in sections, then companies, then the entire battalion, and higher. Which is logical, since all the later and largers stuff is utterly dependent on mastering the individual aspects of drill.
Cheers - Howie