The oldest marine unit in existence has survived five centuries of global conflict

Wars & Conflicts · Published 17 October 2026 Swipe more like this →

In short: Tracing its lineage to 1537, the Spanish Marine Infantry has transitioned from Napoleonic boarding parties to modern amphibious specialists. From the legendary Tercios to the high-stakes operations of the 21st century, discover how this elite corps evolved through empire, revolution, and total war.

The origins of the Spanish Marine Infantry lie in the 16th century. In 1537, Holy Roman Emperor Charles V established the Compañías Viejas del Mar de Nápoles, creating what is recognized as the oldest marine unit still in existence. While Charles V laid the foundation, it was Philip II who pioneered the modern concept of a landing force: a specialized power projection capability capable of fighting effectively from ships while maintaining the ability to strike ashore.

For centuries, the corps' identity was defined by the 'Tercio' structure—a tactical formation composed of one-third musketeers, one/third swordsmen, and one-third pikemen. During the 18th century, the corps expanded significantly. By the mid-1700s, the force comprised approximately 12,000 infantry and 3,000 gunners. Their duties were dual-purpose: they served as boarding parties during an era when ship-to-ship combat relied on hand-to-hand fighting, and they manned the heavy cannons and coastal fortresses.

The 19th and 20th centuries brought radical structural shifts. The rise of efficient naval artillery eventually rendered boarding obsolete, leading to the merger of infantry and artillery into specialized brigades. The corps faced existential threats during the Spanish Civil War, where it split along political lines, with units in Ferrol and Cádiz aligning with the Nationalists while others in Cartagena supported the Republicans. Despite being targeted for disbandment by Republican Minister Manuel Azaña in 1931, the corps survived to modernize, eventually developing the specialized amphibious capabilities and the elite 'Tercio de Armada' (TEAR) seen in contemporary NATO and EU operations today.

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