Desaix had four-cylinder engines fed by 24 Belleville boilers that were designed to produce a total of 17,100 metric horsepower (12,600 kW) intended to give them a maximum speed of 21 knots (39 km/h; 24 mph).

[3] The ships of the Dupleix class had a main armament that consisted of eight quick-firing (QF) Canon de 164.7 mm Modèle 1893–1896 guns.

[1] The nickel steel armor belt of the Dupleix-class cruisers covered the entire waterline length of the ship except for 18.9 meters (62 ft)[4] of the stern.

[6] Named after the French Revolutionary-era General Louis Desaix,[7] the ship was ordered from Ateliers et Chantiers de la Loire on 28 December 1897.

Desaix relieved her other sister, Dupleix, as the flagship of the Atlantic Division in September 1905, but replaced Kléber in the Light Squadron when she returned to the Mediterranean in November 1906.

[11] Improved defenses in the Channel and the stabilization of the front in early 1915 allowed the cruisers to be released from their tasks, so Desaix was assigned to the 3rd Squadron upon her arrival in the Eastern Mediterranean on 16 February.

After 6 June, when the Italians agreed to take over that duty, the cruiser was assigned to reinforce the 2nd DL as it patrolled the area between Capo Colonna in southern Italy and the easternmost point of the Greek island of Crete.

Later that month, she rejoined the 3rd Squadron and was tasked to help blockade the Ottoman coast from Latakia, Syria, to Mersin, together with the protected cruiser Guichen and the seaplane carrier Foudre.

The ships helped to rescue a group of Armenian refugees who were being pursued by the Ottomans from the mountains near Antioch, Syria, on 12–13 September.

[12] The successes of German merchant raiders like Möwe in 1916 caused the Allies to transfer cruisers to the Atlantic to protect their shipping.

Desaix joined her sisters in the newly formed 6th DL in April 1916, based in Dakar, French West Africa.