# Fuerzas sutiles

Fuerzas sutiles ("subtle forces") was an 18th century term, used in the Spanish Empire and its successor states, referring to the strategic usage of small vessels in naval warfare. This included gunboats, xebecs and armed feluccas, originally used to defend ports before being re-purposed to offensive tactics, escorting convoys and operate in seas and rivers.
The concept was popularized by captain Antonio Barceló, after which the Spanish Armada developed it extensively and with great efficacy, turning subtle forces into what has been described as "sea guerrillas". This kind of naval warfare would be known in France as flotilles a l’espagnole ("Spanish-style flotillas").

## Vessels and tactics

Traditional nomenclature in the Spanish Armada included four stages: buques de porte mayor ("major-sized ships" of over 34 guns, like ships of the line and frigates), buques de porte menor ("minor-sized ships" of 16 guns, like corvettes) and fuerzas sutiles (under 16 guns), complemented with the marina corsaria or privateers, including guarda costa. Subtle forces therefore covered a wide variety of vessels and boats, like gunboats, feluccas, xebecs, pontoons, barges, brigantines, fireships, skiffs, pataches, tartanes, zumacas and the increasingly rare galleys and galiots. Due to their small size, their number is often absent from historical records of battles or fleets, but they are conversely recorded to be an instrumental part of the Hispanic naval strategies.
Their main advantages were their speed, lightness, versatility and manoeuvrability, for which they mixed Lateen rigs with rowing and hulls of little draught, allowing them to move with little to no wind, go unnoticed easily and move through paths impassable for larger ships. They were characteristically equipped with a very prominent firepower for their size, with large caliber cannons and howitzers often employing incendiary ammunition. They were also sometimes armored, with recurved armor which along with its small size turned them extremely hard to hit by enemy artillery. The main disadvantage of subtle forces was their vulnerability to bad weather, which could make their usage dangerous or even impossible. In the late 19th century, they were sometimes fitted with steam engines.
Subtle forces were sometimes deployed from either ship, while other times they worked autonomously or were tied to land jurisdiction. They were predominantly used to protect supply lines, attacking bigger ships, conducting night combat and serving as mobile naval artillery.

## History

A possible precedent of the subtle forces is found in the treatise Civitates orbis terrarum by Georg Braun, whose illustration of the Ottoman conquest of Tunis shows Spaniards operating skiffs fitted with cannons in the lake of Tunis, forcing the Ottomans to take a detour.
The true rise of subtle forces comes with Antonio Barceló, who designed gunboats for their usage during the Great Siege of Gibraltar in 1779. His project entailed small boats with sails, rows and oversized artillery pieces, later adding armor too. The first batch featured 40 gunboats and 20 equipped with howitzers, which passed the rest of the siege entering and exiting the bay while bombarding the British positions, especially in night operations. They would become the most effective Spanish active in the otherwise ineffective siege, as recorded by chronicler Frederick Sayer. According to him, Spanish gunboats dealt constant, unanswered damage due to their size and number, as British artillerymen couldn't sight them by night and found out it was similarly useless to aim for their gun flashes.
His gunboats were used in combination with the elaborate, 80-gun floating batteries built by French engineer. Jean Le Michaud d'Arçon. The batteries turned out a fiasco due to their easy targets and inability to approach the coast with their big hulls, to the point that the gunboat division itself had to deploy to cover the retreat and abandonment of the batteries. Despite the siege's failure, the fuerzas sutiles proved their worth enough to be standardized by the Spanish Armada to future engagements, with the gunboats being officially labelled lanchas de fuerza ("force boats")
They were used during the 1972 siege of Ceuta and its 1792 repeat, where subtle forces disrupted Moroccan supply, set fire to their batteries and neutralized several assault, ultimately making the sieges fail.