[1] The sloop of war Catinat under Commander William Le Lieur de Ville-sur-Arce was then at Bangkok waiting to escort the special envoy Charles de Montigny to Vietnam in order to negotiate a new commercial treaty.
[2] The Catinat left Bangkok on 12 August 1856 and arrived before Tourane, the port of the capital, Huế, on 16 September.
The mandarins refused at first to accept them, since the Emperor Thiệu Trị had made it a capital offence for any official to receive a letter from a European.
[3][4] The following day some mandarins came aboard Catinat and offered to make a peace treaty on French terms, but Le Lieur opted to await the arrival of De Montigny.
De Montignty arrived aboard the Marceau only on 23 January, but was refused an audience, Tự Đức having interpreted the departure of Catinat as a victory for himself.