In the negotiations for the Napoleon's marriage to Marie-Louise, the French ambassador in Vienna, Louis Guillaume Otto (1754-1817), played a key role. After playing an important part in the negotiations at Amiens, he was appointed ambassador in Munich in 1803. Then in December 1809 he was sent to Vienna just at the moment when the separation and plans for the marriage plans were at their height. And indeed, Otto was not only to have to negotiate marriage contract but also to field Austrian queries regarding the thorny religious issue of the annulment – an issue of key interest to the very Catholic Austrian party. Once all these technical difficulties had been smoothed over, it was decided to follow the protocols used forty years earlier for the marriage of Marie-Antoinette and the future Louis XVI. On 25 February, 1810, at 7 o'clock in the morning Napoleon decided to speed things up and to direct the organisation of the ceremony by writing directly to his diplomat without passing via the Foreign Minister Champagny as had been the case up to that point:
"Monsieur le Comte Otto, you letter dated 16 only arrived this morning the 25th, at 6 o'clock in the morning. It seems that it was held back crossing the Vosges. The Prince de Neufchâtel [Berthier], who is ready, will leave at ten o'clock with five or six ADCs and a cortège of three of four carriages; but I hope that he travels with sufficient urgency that he arrives in Vienna on the 3rd in the evening. The Duc de Cadore [Champagny] will send all the necessary powers so as to be able to sign the convention as it is requested; I have just read it and cannot see any difficulty which would prevent your signing it. It would not be inconvenient1 for the archduchess to be accompanied by a lady-in-waiting on the journey; I would even prefer a lady-in-waiting to a lady's maid. Since the Strasbourg telegraph informed me on the 22nd, when I was at Rambouillet, that your letter was coming, I immediately dispatched my ADC Lauriston – he should have arrived a long time ago. I am sending you this letter via the duty page so as to get five or six hours on the letter which Duc de Cadore is to send to you and which I will see at my rising. Prepare everything that needs to be prepared, both for the entrance and presentation of the Prince de Neufchâtel, and spare no expense so that everything is done with fitting magnificence. We have here the list of the gifts which the King offered on the Delivery of the Dauphine in Strasbourg;2 we shall send the same for the Delivery of the Princess at Braunau. The Prince de Neufchâtel will not offer any presents. We have not found any evidence that such presents were offered in Vienna. However, if it was the custom, please be quick to inform the Prince de Neufchâtel and to provide something. I am assuming that it is a mistake in the note where it seems to imply that the archduchess must marry her brother.3 I do not think that the Prince imperial has reached the age of majority; but since, as Monsieur de Metternich desires, the letters are sent with the names and addresses left blank, you may tell Monsieur de Metternich that the Emperor may appoint whoever he wants. If age is no object, I would prefer it to be the archduchess's brother, who will be emperor one day. If his lack of majority is a problem, I would prefer it to be Prince Charles; but I'm sure that you understand that with the family so divided as it is, I shall not make a special request. Ask around in the country to find out whether it would not be suitable for the Prince Charles to perform this duty. If the nomination of the Prince Charles is not agreeable to the emperor, he could appoint the Archduke Reinier. For the rest, the Emperor can act in this respect as he like, and I will accept the choice he makes. You will find, in the Moniteur here enclosed, the composition of the Empress's household. I have not appointed any new Ladies-in-Waiting, although it is my intention to provide her with seven or eight of the Empress's age, but I shall not do this until she arrives in Paris. Once the Prince de Neufchâtel has performed his duties as ambassador extraordinary, he should go to Braunau to receive the Princess. In two days time, the Lady of Honour,4 the Dame d'atour,5 four Ladies-in-Waiting, the Chevalier d'honneur,6 the Premier écuyer,7 four chamberlains and four pages with a Maréchal des logis and all the necessary personnel are to leave for Braunau, where the Delivery of the Princess will take place, and they will be back here on 8 March.8"9
After completing this most prestigious of missions, Otto remained in his post in Vienna until 1813. Otto's archives, carefully assembled over the years, were in part destroyed in 1814 when his home in Villers-Cotterêts was pillaged. His death in 1817 came before any publication of his memoirs had been possible, and his descendants gave all his letters from Napoleon that remained in his possession to General Pelet. This historian and archivist10 published these documents in Opinion de Napoléon sur divers sujet de politique et d'administration (1833). For some, including the item mentioned above, this was to be their only publication to date. Since 1833, documents from the "Otto collection" have appeared all over, in various different auctions.11 The Fondation Napoléon correspondence project has thus far collected thirty-five letters from Napoleon to Otto, which date from 1804 to 1810, and which have been published (or remain to be published12) in the various volumes of La Correspondance générale de Napoléon Bonaparte.