The idea of a circular battleship emerged in a 1868 report from Scottish shipbuilder John Elder and evolved by the Royal Navy's Edward Reed but not officially realized until Rear-Admiral Andrei Popov of the Russian Navy pressed home the concept. The design revolved around a shallow-draft vessel capable of traversing low-level waters such as rivers and lakes, giving it proper access to more battlefronts than traditional well-armed warships could ever reach. The concept also spread out the displacement of both armor and armament, leading to a (theoretically) more powerful warship than possible through conventional designs. The end result, however, became one of the most panned warships ever completed - the "Novgorod" which was to represent a class of such ships. Its circular hull did allow for the expected armoring and armament benefits but it suffered from stability in anything more than calm waters and accuracy of its main armament was left wanting.
Only one example of this unique, and mostly forgettable, ship was built for the Russian Navy.
The Novgorod was intended as a new class of Russian monitors to help protect Black Sea and Dnieper River positions. She was named after the Russian city of Novgorod and constructed by the New Admiralty Shipyard of Saint Petersburg from the span of 1871 until 1874. Her keel was laid down on December 29th, 1871 and she was launched to sea on June 2nd, 1873. Completed in 1874 she began formal service with the Russian Navy.
Originally Novgorod was developed along the lines of a monitor ironclad. Her dimensions included a length of 101 feet with a beam equaling that while her draught was just 13.5 feet. Displacement was 2,500 tons (long) and power was from six compound-expansion steam engines fed by eight boilers - all this driving six shafts (the outboard pair were removed in 1876-1877 due to their minimal propulsion benefits). At best, the ship could hope to make upwards of 6.5 knots in ideal conditions.
Two smoke funnels - one at port side and the other starboard - were fitted along the sides of the circular shape with the main armament seated at direct center. The wheelhouse was fitted over the rear section of the circle (added between 1873 and 1874) and elevated walkways ("bridge wings") were featured as extensions from the funnel towers. A large-area superstructure (housing crew quarters) was added to the bow section and hand rails ran around nearly the entire diameter of the hull. Primary armament was 2 x 11" (280mm) guns though, while rifled, remained muzzle-loading weapons. A rotating turntable gave the guns their inherent traversal and could be aimed and fired jointly or independently of one another. Provisions were also made for carrying a "spar" torpedo weapon. Armor protection ranged from 9" at the belt to 9 inches at the barbette. The deck offered up to 2.75" of protection.
Novgorod's first, and only real, call-to-arms came during the Russo-Turkish War (1877-1878) where she was stationed at Odessa to act as a floating deterrent. Additional armament was added at about this time, this in the form of 2 x 4-pounder (3.4") cannon to improve her all-around defense - particularly against enemy torpedo boats which had grown to become a primary threat to capital ships. The war ended in March of 1878 with a Russian-Coalition victory.
In the post-war period, armor was added to her engine area and the main gun battery. In 1892 she was redesignated a "coastal defense ironclad" and had 2 x 37mm cannons added. From then on she made a few cruises in good weather periods but eventually deteriorated to the point that her services were no longer needed. She was struck from the Naval Register in July 1903 and sold for scrapping before the end of 1911.
Thus ended the idea of a circular metal-clad warship.