When the Marine Nationale mobilized in anticipation of war on 1 August, the Division de complément was ordered to Algiers, French Algeria, to protect the convoy route to Metropolitan France. They conducted their first escort mission on 6 August before arriving at Bizerte, French Tunisia, on the 22nd where they began conducting contraband patrols in the Sicilian Narrows. In September "Suffren" was fitted with additional Barr and Stroud rangefinders near the bridge. Two of these were mounted on transverse rails fore and aft of the bridge. The after bulkhead was removed and the two 100-millimetre guns on the side of the superstructure were moved one deck lower. Guépratte complained that his ships were not well suited to such a mission and he was ordered to take "Suffren", the predreadnought and the torpedo cruiser to Port Said, Egypt, to escort troop convoys from British India on 23 September. The following day he was ordered to rendezvous with the semi-dreadnought at the island of Tenedos where he was to place himself under the orders of the British Vice-Admiral Sackville Carden to assist British ships in blockading the Dardanelles to prevent any sortie by the Ottoman battlecruiser and the light cruiser back into the Mediterranean. The Division de complément was renamed the Division des Dardanelles (Dardanelles Division) to reflect its new role. On 3 November the two French battleships joined British ships bombarding the Ottoman fortifications at the mouth of the Dardanelles. The short bombardment by the Allies, during which "Suffren" fired 30 shells from her main guns, did little damage, but alerted the Ottomans that their defences there required strengthening. After the predreadnought arrived on 16 November "Suffren" sailed for Toulon for a lengthy refit.