The Imperial Guard (French: Garde Impériale) was originally a small group of elite soldiers of the French Army under the direct command of Napoleon I, but grew considerably over time. It acted as his bodyguard and tactical reserve, and he was careful of its use in battle. The Guard was divided into the staff, infantry, cavalry, and artillery regiments, as well as battalions of sappers and marines. The guard itself as a whole distinguished between the experienced veterans and less experienced members by being separated into three sections: the Old Guard, Middle Guard and Young Guard.
The Guard had its origin in the Consular Guard (Garde des consuls), created November 28, 1799, by the union of the Guard of the Directory (Garde du Directoire exécutif) and the Grenadiers of the Legislature (Grenadiers près de la Représentation nationale). These formations had for principal purpose the security of the executive and legislative branches of the French Republic and gathered a small number of soldiers, about a thousand. One may question their utility, as they did not oppose Napoleon's 18 Brumaire coup of 1799. The Consular Guard changed its name to the Imperial Guard on May 18, 1804. Its headquarters were located at the Pentemont Abbey in Paris.
Napoleon took great care of his Guard, particularly the Old Guard. The Grenadiers of the Old Guard were known to complain in the presence of the Emperor, giving them the nickname Les Grognards, the Grumblers. The Guard received better pay, rations, quarters, and equipment, and all guardsmen ranked one grade higher than all non-Imperial Guard soldiers. Other French soldiers even referred to Napoleon's Imperial Guard as "the Immortals".
The Guard played a major part in the climax of the Battle of Waterloo. It was thrown into the battle at the last minute to salvage a victory for Napoleon. Completely outnumbered, it faced terrible fire from the British lines, and began to retreat. For the first (and only) time in its history the Middle Guard retreated without orders. At the sight of this, Napoleon's army lost all hope of victory. The Middle Guard broke completely but the Old Guard (and some of the Young Guard) battalions held their formation and secured the retreat of the remainder of the French Army before being almost annihilated by British and Prussian artillery fire and cavalry charges.