From what I know the Wehrmacht in 1941 had somewhere around 3 million men invading into Russia. Just how exactly did all of this occur in the first week or so of the war? How with 1930's type communication and basic paper maps did everyone keep on plan? How far apart were divisions or armies spread out from one another? did armies all move at once in a day or did it take days just to move a entire few divisions and wait for the rest to catch up? Was it mostly through radio communication or by cars/bikes and horses also?
Im assuming in between the front stopping, attacking, counter attacking it was very confusing at times trying to let the rear know where and how to set up while communicating with other divisions or regiments and such as if a Artillery unit had to move up or panzer battalion and who to pick and what. And with it being war it had to change day in and out going town to town or when crossing a major river and then at times Im sure weather and bad radios messed up a lot of things. And then not to mention Logisitics. Where exactly were the food trucks and such kept and far from the front line? and how often in the week did the soldiers refresh their rations? (Sorry for all the questions but just so mind boggling)
This is a really good and big question and like most good questions it has a complex answer.
The key thing you're really asking about here is the general staff. The general staff is the administrative backbone of an army and its goal is managerial in nature. The problem with Germany in WW2 is that one of Hitler's preferred way to keep power centrally in his hands was compartmentalisation. Germany had many competing departments and orginisations with overlapping remits. These would all compete against each other for Hitler's approval. The military was no different and there were two departments that fought for control during the war. These were the Oberkommando der Wehrmacht (OKW, "High Command of the Armed Forces", which means all three services) and the Oberkommando des Heeres (OKH) which was the high command of the Heer or land forces.
These two organisations had hundreds of departments and sub-departments which covered every conceivable aspect of military endeavour. They produced outlines for potential future operations, analyses of previous operations, strategic advice, available resources and operational orders once strategy has been decided. Once a strategic goal had been decided, in the case of Barbarossa that goal was the elimination of the Soviet State through the rapid destruction of its field armies, the staff went about discovering how that could be achieved with the resources available. They looked past campaigns, in Poland, the Low Countries and France, but also at WW1 and even as far back as Napoleon's 1812 campaign. Quartermasters worked together with railways experts and logistics officers to figure out what the likely needs of an operation of the size and scope of Barbarossa would be. The requirements of panzers, infantry, artillery, engineers and all the rest would be worked out along standard lines laid out in pre-war manuals and estimates, possibly reconsidered after the Western campaigns, but not always.
Railways were the best method for moving large amounts of war materiel and supplies, something that was relatively straightforward in western Europe where the railway gauge was standardised. The USSR however used a different gauge size, meaning that as the Germans moved into the USSR they would leave behind their railheads and most of their supplies. To move them forward the railway lines would have to be shrunk or they would need to use Soviet trains, something the Soviets were able to largely deny the Germans. Given that Barbarossa was an attack in great breadth as well as depth it mean that thousands of miles of railway line would have to be changed to German size.
In the case of Barbarossa and the IMMENSE size of the USSR and the huge numbers of troops that would need to be supplied the OKH scrambled to find a way to make up the shortfall in logistic support until the railways could be brought forward. This meant more trucks. But Hitler had demanded the expansion of the motorised forces of the Wehrmacht and it meant that thousands more trucks had to be found. German production wasn't able to outfit them so they looted their newly conquered territories to supply trucks to their armies. This in itself shows one of the huge problems encountered. Militaries try to standardise vehicles and parts so as to keep the number of replacement parts down. With the addition of tens of thousands of civilian vehicles of hundreds of different types this meant the number of different parts required to keep them moving skyrocketed to over a million different replacement parts. [1]
Trucks were also stripped from infantry units for the new motorised formations and replaced with horses and carts, dramatically expanding the amount of fodder and veterinary services required for these formations.
To bring this back to the staff, units and formations would have their own staff who were responsible for all of these different areas. The larger the formation, the more staff officers who would be part of the headquarters to coordinate all of these disparate parts and hopefully keep them running smoothly.
Next part will be about controlling operations and communications.
[1] This is the only number i remember exactly but for much much more detail about the many logistical problems faced by Barbarossa see David Stahel - Operation Barbarossa and Germany's Defeat in the East.