1st King's Immemorial Infantry Regiment of AHQ

Regimiento de Infantería Inmemorial del Rey n.º 1 (1st King's Immemorial Infantry Regiment)
Coat of Arms of the 1st King's Immemorial Infantry Regiment
Active	1248–present (768–769 years)
Country	Spain
Branch	Ejército de Tierra
Type	Grenadiers/Fusiliers
Role	Honor Battalion – Public Duties Support Unit – Security/Administration Service Unit – Engineering Support Band Unit – Music
Size	4 battalions
Garrison/HQ	Madrid
Commanders
Commander in Chief	HM The King

The King's Own Immemorial 1st Infantry Regiment of the Spanish Army is claimed to be the oldest continuously operating military unit in the world, although there is no proof of this. King Ferdinand III of Castille, in 1248, during the conquest of Seville, with some of his men-at-arms, assaulted and took a tower. Seemingly, with such boldness and bravery they gained the admiration of the King. The campaign finished and with the consequent disbandment of troops, King Ferdinand decided to permanently keep that force on the rolls, making one of the first standing armies in Europe since the Roman Empire.

On 28 August 1632, on the initiative of Philip IV, a special Corps of troops was ordered to be formed with veteran soldiers, reenlistments and Knights of noble ancestry - men so skilled that they only took arms when the Monarch assumed command in person, designating it "King's Guard Colonelship." Its organization commenced in Almansa in 1634, its force fixed at fifteen companies with 90 harquebusiers, 40 musketeers, and 60 corslets and pikemen each. Later, in 1638, it was augmented to twenty. Its first Colonel, Count Duke of Olivares, Don Gaspar de Guzmán, whose post was the recently created "King's Guard Colonelship," was in command of very distinguished soldiers of great renown. In 1640, Philip IV elevated it to the category of King's Guard Regiment and in 1664 to Castile Tercio. From 1701 to 1710 it was dedicated to its ancient mission, guarding the Monarch, and it was in 1707 when it received the designation Castile, and in 1710 that of Castile Immemorial Infantry Regiment. It gained glory in the Spanish War of Succession and the Italian Campaigns (1718-1749), eventually it received the name King's Infantry Regiment on 7 January 1766. That same year, King Charles III, persuaded by the antiquity of the Regiment, declared it the King's Immemorial.