The Oath of the Army after the distribution of the Eagles on the Champs de Mars, December 5, 1804 Jacques-Louis David (1748-1825)

The picture has something of this: people, group, wear, music, weapon, man, many, military, war, cavalry, veil, festival, outfit, soldier, battle, performance.
Perhaps it’s a painting of a large group of people standing in front of a crowd of men and women, all dressed in military garb and holding flags.