[2] While more lightly armed and armored than many of the cruiser's contemporaries, her small size and relatively simple design facilitated the vessel's construction and her relatively high speed made the ship useful for many military operations.

On 18 February 1904, under the orders of Admiral Itō Sukeyuki, Suma arrived in Shanghai with the cruiser Akitsushima to compel the disarmament of the Russian gunboat Mandzhur, or the ship's destruction under the international norms for neutrality, accomplishing her mission by 31 March.

In early May, Suma covered landings by the Japanese Second Army in Manchuria, following which (on 15 May), she assisted in the rescue of survivors from the crew of the ill-fated battleships Hatsuse and Yashima after those ships struck naval mines off the coast of Port Arthur.

On 7 June, Suma, together with the gunboats Uji, cruiser Akashi and a detachment of destroyers entered the Gulf of Bohai to support the landings of elements of the Japanese Second Army, and later bombarded Russian shore installations and a railway line along the coast of Manchuria.

During the first day of the battle, Suma and Chiyoda attacked on the left flank (southern portion) of the Russian formation, capturing transports and the hospital ships Orel and Kostroma.

Later that day, Suma and Chiyoda attacked the cruisers Oleg, Aurora, Vladimir Monomakh and Dmitrii Donskoi and sinking the already damaged battleship Knyaz Suvorov and repair ship Kamchatka.

The following day, 28 May, Suma reported the surrender of the remaining ships under the command of Rear Admiral Nikolai Nebogatov, and unsuccessfully pursued the cruiser Zhemchug, which managed to escape the battle.

[5] Afterwards, Suma was assigned to the Japanese force, which seized Sakhalin from Russia, covering landings by the IJA 13th Division at several locations, and securing lighthouses and port facilities.

She was later based in Singapore together with Yahagi, Niitaka and Tsushima and a flotilla of destroyers, and reassigned to provide coastal defense to Australia and New Zealand, as part of Japan's contribution to the Allied war effort under the Anglo-Japanese Alliance.