Hi, I am about to write an novel about a man in the Napoleon era. But one thing really bothers me is that I have absolutely no clue about the army organisation in the Napoleon era. I know the modern army organisation is like Army Group>Army>Corps>Divisions and so on... Is the organisation in the Napoleon era the same? or more simpler? Do they have something special compare to the modern army? How do they arrange their army? If they are fighting in lines, do they have platoons or fire squads? Do all the country organised in the same way?(same arrangement?) . Also, how do generals communicate on the battlefield, or even in a country when they are miles and miles away to commence an operation or a synchronized pincer movement?
So, Napoleon implemented and was the founder of the corps system. Beyond that, there was no larger military formation than army, of which Napoleon would command. There were other armies, such as in Spain, but they would never have a clear command structure because Napoleon never trusted his generals with independent command for too long.
Beyond that, it would be very similar to what you describe, from corps to platoon, the organization is similar although the numbers may be different. However, this is just the French army and I can't speak very much about the different armies beyond a few basic facts.
Before reforms were made, most armies were organized no larger than a division. The division general would have to write orders to individual regimental commanders, their battalion commanders, and hope that they would all follow the orders. In the French system, Napoleon would make orders to his Chief of Staff, Louis-Alexandre Berthier, who acted as the magnifier to Napoleon's orders. He would translate whatever scribble Napoleon wrote or said to proper orders for the entire army, from which he would have aides go forth from the HQ to the corps commanders. From there, orders would trickle down the command structure, making a far more efficient series of orders for the Grande Armee.
On the battlefield, orders would often be communicated by messenger. However coordination was rarely achieved and most battles were "planned" out the morning of, with orders given to corps commanders to achieve X goal (such as taking Y area or pushing Z flank). How they did it, Napoleon didn't care because it would be done.
With success over the armies of Europe, many commanders (such as Scharnhorst and Archduke Charles) looked to Napoleon and attempted to do the same. Both the Prussian and Austrian militaries would reform to copy many of Napoleon's organizational methods in order to become more efficient on the battlefield. While Napoleon did end up falling due to a variety of reasons, one reason that is most prominent is how many of his enemies adopted the same ideas that Napoleon depended upon for victory.