Actually its a bit of a controversy about which units are the oldest. All of these are still current and fairly large with multi Battalions: King's Own Immemorial Regiment of Spain, formed in 1248. The French 1st régiment d'infanterie de ligne, created from the ancient "bandes de Picardie" first established in 1479. Swedish Life Guards formed in 1521. I think more claim ancient lineage too. Joe Sweeney