The Troude class was a group of three protected cruisers built for the French Navy in the late 1880s and early 1890s.

The Troude-class cruisers were intended to serve as flotilla leaders for the torpedo boats, and they were armed with a main battery of four 138 mm (5.4 in) guns.

All three members of the class served in the Mediterranean Squadron in their early careers, where they took part in routine training exercises.

Cosmao remained in reserve until the start of World War I in August 1914, when she was recommissioned to patrol the coast of French Morocco.

Beginning in 1879, the Conseil des Travaux (Council of Works) had requested designs for small but fast cruisers of about 2,000 long tons (2,032 t) displacement that could be used as scouts for the main battle fleet or to lead squadrons of torpedo boats.

[1][2] In the early 1880s, the Jeune École doctrine, which envisioned using a combination of cruisers and torpedo boats to defend France and attack enemy merchant shipping, became popular in French naval circles.

In early 1886, the Jeune École supporter Gabriel Charmes published his book La réforme de la Marine (The Reform of the Navy), in which he called for small commerce raiding cruisers armed with a pair of 138.6 mm (5.46 in) guns—sufficient for the task of sinking merchant vessels—and a speed of 20 knots (37 km/h; 23 mph), which would allow them to escape any stronger vessel.

The following day, de Bussy submitted a set of specifications to meet Aube's requirements; these included a speed of at least 19.5 knots (36.1 km/h; 22.4 mph), a range of 2,400 nautical miles (4,400 km; 2,800 mi) at a speed of 10 knots (19 km/h; 12 mph), two 138.6 mm guns, and a 40 mm (1.6 in) curved armor deck.

Over the following month, de Bussy prepared a more detailed design based on these specifications, which Aube approved on 20 March.

Five yards responded by 30 April 1886, and the proposal from Jean Baron, the chief engineer at Forges et Chantiers de la Gironde, was selected; this vessel became Troude, the first member of the Troude| class.

Their hulls had a pronounced ram bow and tumblehome shape that characterized most French warships of the period.

[6][7] The ships' propulsion systems were manufactured by Schneider-Creusot and consisted of a pair of horizontal compound steam engines driving two 3-bladed, bronze screw propellers.

During construction, Troude and Cosmao were modified with an armored conning tower with 40 mm sides, though Lalande did not receive this alteration.

In 1893–1894, Troude and Lalande had their cofferdams replaced by a layer of highly sub-divided watertight compartments that covered the entire width of the deck.

[22] Cosmao was recommissioned in August 1914 after the start of World War I and tasked with patrolling the Moroccan coast, though she saw no action.