I agree with previous comments that Marbot’s writings need to be read carefully and verified by other sources, because they are a mixture of fact and fantasy. I have noticed this in my own research on the Battle of Waterloo (unfortunately not covered in his memoirs), and thought you might be interested in the following account (the next 7 paragraphs) by the Belgian historian Bernard Coppens on his website concerning the accuracy of Marbot’s writings about 1815 (https://www.1789-1815.com/marbot1.htm). I have translated this into English, but if you wish to read the original French version, use the link above.
“Marbot, who as commander of the 7th Hussar Regiment occupied a key position on the right of the French army, is an important eyewitness for the Battle of Waterloo. Placed to the right of the 1st Corps, he had a front-row seat for seeing the arrival of the Prussians. But his account written in 1815 is formal: "I was told that Grouchy would arrive, but it was Bülow who deployed … and this was a surprise." Marbot should have conducted a reconnaissance on the right. If he did not, it was because he had contrary instructions, and this was because the French Army, and its head, had not the slightest hint of the menace that was advancing on the right.
We have several accounts written by Marbot, notably a letter written on 26 June 1815 and another written to Marshal Grouchy in 1830. One can see that the two letters give completely different accounts of the events. In the one written immediately after the battle, Marbot states that he was on the right flank of the army, waiting to see Grouchy’s troops arrive, and was surprised to see Bulow deploying [instead]. If one believes this version, then he was not sent out to reconnoiter towards Mousty and Limal, as he states in 1830. The two versions are so contradictory that one of them must not correspond to the truth.
Marbot wrote in 1830 that he made a report at the request of Davout and this document could be found in the military archives. This document has disappeared, and it is not certain that this is by accident: most original documents on Waterloo have disappeared mysteriously.
Fortunately we still have the memoirs of a squadron commander of the 7th Hussars, Major Dupuy, and the memoirs of Colonel Bru, who saw Marbot on the 4th of July in Paris. One can see from these memoirs that it is the first version by Marbot, the one written in 1815, that seems closest to the truth.
Was Marbot lying in 1830? For what reason? Could the 100,000 francs that Napoleon left to him in his will in order to engage in writings “for the defense of the glory of the French armies and to confound the liars and apostates” have pushed him into distorting the truth in order to have his own remembrances conform to the Memoirs of Napoleon?
One notes – and regrets – that the memoirs of Marbot, edited with such verve by the fiery general, stop in 1814. Is this because death interrupted his work or because the subject, in view of its importance, was too difficult to treat? Or was it his editors who judged it best not to publish this section?”
- - - That is the end of my quote from Bernard Coppens’ website. For more details on his research about Napoleon and Waterloo see his books “Waterloo: les mesonges. Les manipulations de l’histoire enfin révèlées” [Waterloo: The Lies. The Manipulation of History Finally Revealed] (2009) and the shortened and revised version “Waterloo: l’histoire vraie de la bataille [Waterloo: The True History of the Battle] (2015) , plus his contributions to the early volumes of the series “Waterloo 1815: Les Carnets de la Campagne”. While I do not always agree with all of Bernard’s arguments regarding Waterloo, his refutation of Napoleon’s claims that he knew early on that the Prussians were coming to Waterloo and took appropriate measures to deal with this threat are certainly supported by all the Prussian accounts I have read. They state that the French were completely unaware that the Prussians had arrived on the battlefield and only reacted after Bülow’s attack began. And Bernard also shows that Marbot's 1830 account of his supposed actions far to the east of the French army at Waterloo are pure fiction.