The mass, along with maneuvers, are the big moments in the Imperial army's stay at Chalons. The masses were the occasion for an unusual deployment of troops and a number of accounts relate with lyricism and emotion the grandiose character of this ceremony that was punctuated with blasts of canon and celebrated before 20,000 men in full uniform kneel down on command with the elevation of the host, and singing with one voice the Domine Salvum. "The mass," wrote one observer from the region, "is one of the most moving sights imaginable. I have seen serious non-believers deeply touched. It is simple, it is beautiful, it is grand, it is worthy, in a word, of the catholic faith".
Mass was celebrated outside with an altar was rented in 1857 from Godillot. It drew a huge crowd, even more when the Emperor and Empress were present : 30,000 visitors were registered at the camp on Sunday September 20, 1857.
The Empress who stayed at the camp of Chalons from October 2nd to 8th, went to mass on the 4th. She was seen seated before the altar "dressed in a simple white robe and a small round hat decorated with black and white feathers and lace". Behind the Empress, her ladies in waiting, Madams de Montebello and de La Bédoyère, preceded the marshalls, the generals and staff officers of the camp. The mass was followed by the general march of the troops returning to their billets, passing before the Emperor, his guests and his staff assembled on the steps of the imperial pavilion.