I just talked a bit about the specific mechanics of how orders were given and delivered here, and I'll expand from some of those points to talk about the overall system of command and control on a Napoleonic battlefield. The basic problem of the system is how one man can command tens of thousands of men – many of whom, thanks to the smoke of the battlefield and the lay of the land, he might not even be able to see - with no communications faster than a written or verbal order delivered by a man on horseback.

To understand the Napoleonic system of control, we need to go back to pre-revolutionary France, particularly to the Royal Army during the Seven Years' War. The defeats France suffered precipitated a massive array of theoretical and practical work in the military minds of the Royal Army, all of it focussed on improving the army so it would be able to fight effectively in the next war it fought. One of these concepts was the division. During the Seven Years' War, French generals had no permanent formations above the Regimental (two battalions – although these might not fight together) level, and no real transitory ones above the brigade (two regiments, or four battalions). It was common – not just in the French army – for commanders to have to issue orders to each brigade, and sometimes to each regiment.

This made command and control of an army difficult, because a major attack might require issuing orders to multiple subordinates at once, which might not get there at the same time or get there at all. It also made independent manoeuvre of multiple parts of the army very difficult to coordinate, since the staff-work required to handle it was long and complicated. Further, there was no real defined chain of command – a sufficiently noble officer might successfully defy the orders of a less-noble superior, especially if they had the favour of the King.

Along with the famed Gribeauval System and the development of ideas about attacks in column rather than line, French theorists came up with the idea of the division – a group (three to seven) of brigades, supported by its own staff, which could act en masse in battle. This didn’t see much useful implementation in the Royal Army after its formal introduction in 1776, but it formed a theoretical basis for the system under the Revolution. Revolutionary divisions were typically composed of infantry, cavalry and artillery, but Revolutionary generals were typically not particularly competent as cavalry commanders, and command of a given division was often temporary, making a general’s authority open to question. Divisional staffs were not overly competent, and they were often large enough to get themselves into trouble but too small to fight their way out of it. That said, it had advantages: divisions could manoeuvre independently and live off the land – essential, given the awful state of French logistics in this period – and concentrate for battle when needed, and it made the staff-work of French generals much simpler compared to that of their opponents.

Napoleon (building on the work of Lazare Hoche) developed the divisional system into the corps d’armée system in 1800, and refined and solidified this in the years the French army spent in the camps along the Channel coast. The basic idea was the same as the division: a large formation that could march, forage and fight independently, concentrate with its fellows for battle, and provide a relatively easy way to command the huge Grande Armée. Each corps was made up of multiple divisions (now reformed – infantry and cavalry formed separate divisions; divisions had their own artillery, whose deployment was at the discretion of the divisional general) with a central reserve of artillery under the supervision of the corps commander. Each corps was at least 20,000 strong in theory – large enough to defend itself against a much larger force until reinforcements could arrive – and capable of independent scouting and intelligence work if necessary. This system allowed Napoleon to command over a hundred thousand men across the entirety of Europe during the Napoleonic Wars, and was almost universally copied by his opponents.

Napoleon gave one cavalry brigade or so to each corps, almost always composed of light cavalry, for scouting purposes and occasional battlefield use. Most cavalry was kept in the cavalry reserve – usually under the command of Marshal Murat – where it could be committed in a single overwhelming mass or deployed by division as necessary. There was also a central artillery reserve under Napoleon’s personal command, although this was often a more informal organisation, consisting of the Guard artillery and the artillery reserve of whichever corps was designated as the masse de decision (the reserve whose job it was to punch through the weakest point in the enemy army after all its forces were committed). The Imperial Guard also formed a separate corps, although its cavalry and artillery typically operated as part of their respective reserve.

From that basis, we can move on to look at the way orders would be issued. Napoleon gave orders to the corps commander; the corps commander then gave orders to his divisional generals, who then gave orders to their brigade or battalion commanders as necessary. Napoleon would ideally give specific objectives to corps commanders, making it clear what his wishes were. It was the corps commander’s job to deploy his divisions in such a way as to achieve this objective (occasionally Napoleon would indicate what he wanted done with specific divisions, but most orders were given at the corps level to ensure that moves were made in force). A divisional commander was responsible for the deployment of his battalions or squadrons and artillery, and, once given an objective, it was his job to determine how best to deploy his forces to achieve that objective.

How much control a senior officer had over a specific unit depended on the situation; a corps commander might order a specific formation for a division before an advance, but once the firing started and the division was out of earshot, responsibility fell on the divisional general. This also applies to corps commanders: if they saw an opportunity or were confronted with an unforeseen development, they were expected to take the initiative and adapt to the circumstances in such a way as to best achieve the initial objective the Emperor had set for them and achieve their part in the battle plan, which Napoleon would have shared. Lower-ranking commanders would also be aware of the general objective, so that they could take over if their immediate superior was killed.

Thus, a general could issue an order to a corps commander to hold or advance against a general point - Davout to hold the right between Zokolnitz and Telnitz; Soult to storm the Pratzen heights and break the Allied centre; Paget to repel the French attack near La Haye Sainte – and leave the specifics up to that commander. Often, generals would position themselves near a crucial point so that their orders would be quickly relayed – Napoleon always endeavoured to put himself near his reserve so he could time their advance and the commitment of the artillery reserve precisely – and occasionally took personal command of forces in the crucial moment – Davout led his corps reserve artillery forward at Auerstedt, Wellington ordered the Brigade of Guards and the 33rd forward to repel the Imperial Guard at Waterloo. Napoleon also had aides-de-camp who ranked as generals of division – the highest rank in the French army – who could be detached for specific missions if necessary, and could reprimand or overrule any commander – sometimes up to and including the Marshals – to achieve the Emperor’s will.

Command, therefore, was quite devolved by necessity, and manoeuvre off the battlefield was controlled by dint of considerable staff work and hard riding by staff officers. It was a highly-organised and graded system that, mainly, was developed by the French and then copied and improved upon to differing degrees by France’s enemies.

Principal sources:

The Campaigns of Napoleon by David Chandler

Swords Around a Throne: Napoleon’s Grande Armée by John R. Elting