Azuma (吾妻) (sometimes transliterated (archaically) as Adzuma) was an armored cruiser (Sōkō jun'yōkan) built for the Imperial Japanese Navy (IJN) in the late 1890s.

The 1896 Naval Expansion Plan was made after the First Sino-Japanese War, and included four armored cruisers in addition to four more battleships, all of which had to be ordered from overseas shipyards as Japan lacked the capability to build them itself.

Unlike most of their contemporaries which were designed for commerce raiding or to defend colonies and trade routes, Azuma and her half-sisters were intended as fleet scouts and to be employed in the battleline.

[6] The main armament for all of the "Six-Six Fleet" armored cruisers was four Armstrong Whitworth-built 45-caliber eight-inch guns in twin-gun turrets fore and aft of the superstructure.

[13] The contract for Azuma, named after the Kantō region,[14] was signed on 12 October 1897 with Ateliers et Chantiers de la Loire, and the ship was laid down at their shipyard in Saint-Nazaire on 1 February 1898.

Tōgō chose to attack the Russian coastal defenses with his main armament and engage the ships with his secondary guns.

[19] Although many ships on both sides were hit, Russian casualties numbered some 150, while the Japanese suffered roughly 90 killed and wounded before Tōgō disengaged.

[20] In early March, Vice Admiral Kamimura Hikonojō was tasked to take the reinforced 2nd Division north and make a diversion off Vladivostok.

While scouting for Russian ships in the area, the Japanese cruisers bombarded the harbor and defenses of Vladivostok on 6 March to little effect.

The two units narrowly missed each other on the 24th in heavy fog, and the Japanese proceeded to Vladivostok, where they laid several minefields before arriving back at Wonsan on the 30th.

[21] The division failed to intercept the Russian squadron as it attacked several transports south of Okinoshima Island on 15 June, due to heavy rain and fog.

The arrival of the Russians off Tokyo Bay on the 24th caused the Naval General Staff to order Kamimura to sail for Cape Toi Misaki, Kyūshū, fearing that Jessen would circumnavigate Japan to reach Port Arthur.

The General Staff finally ordered him back to Tsushima Island on the 30th; later that day he received word that Jessen's ships had passed through the Tsugaru Strait early that morning and reached Vladivostok on 1 August.

[22] On 10 August, the ships at Port Arthur attempted a breakout to Vladivostok, but were turned back in the Battle of the Yellow Sea.

36 miles (58 km) north of the island he encountered Kamimura's squadron, which consisted of four modern armored cruisers, Iwate, Izumo, Tokiwa, and Azuma.

[23] Jessen ordered his ships to turn to the northeast when he spotted the Japanese at 05:00 and they followed suit, albeit on a slightly converging course.

Jessen turned southeast in an attempt to open the range, but this blinded the Russian gunners with the rising sun and prevented any of their broadside guns from bearing on the Japanese.

Kamimura circled Rurik to the south at 08:00, then allowed the other two Russian ships to get to his north and gave them an uncontested route to Vladivostok.

They fought a running battle with the Russians for the next hour and a half; scoring enough hits on them to force their speed down to 15 knots (28 km/h; 17 mph).

[25] About 10:00, Kamimura's gunnery officer erroneously informed him that Izumo had expended three-quarters of her ammunition, and he turned back after a five-minute rapid-fire barrage.

[26] On 30 December, Azuma and the armored cruiser Asama were ordered to patrol Tsugaru Strait to prevent any blockade runners from reaching Vladivostok.

[27] As the Russian 2nd and 3rd Pacific Squadrons approached Japan on 27 May, having sailed from the Baltic Sea, Yakumo was assigned to Kamimura's 2nd Division of the 2nd Fleet.

The Russians were spotted by patrolling Japanese ships early that morning, but visibility was limited and radio reception poor.

[28] Azuma was second of six when Tōgō opened fire on the 2nd Pacific Squadron at 14:10 and, unlike most of the ships in the division, initially engaged the battleship Knyaz Suvorov.

[32] On 14 June, Azuma (along with Yakumo, the armored cruisers Nisshin and Kasuga) was assigned of the 3rd Fleet, under the command of Vice Admiral Kataoka Shichirō, for the capture of Sakhalin in July.

Azuma was briefly relieved of her assignment from 1 May to 1 December before beginning another training cruise to North America and Hawaii, together with Asama, on 20 April–11 August 1914.

[34] In early 1917, Azuma was dispatched on a diplomatic mission to return the body to the United States of George W. Guthrie, the Ambassador to Japan, who had died while in office.

[37] Azuma was refitted again in 1930; this included replacement of her boilers that reduced her horsepower to 9,400 ihp (7,000 kW) and her speed to 16 knots (30 km/h; 18 mph).