In 1248, King Ferdinand III of modern-day Spain successfully completed the Siege of Seville — part of the ongoing effort to reclaim the Iberian Peninsula from Muslim rule — with the assistance of a plucky fighting group known as the Band of Castile. Said to be impressed by the bravery of this band of fighters, Ferdinand designated it a permanent division under his service, thus inaugurating what is now regarded as the world’s oldest active military unit. The unit was reorganized numerou...
