Omaha class cruisers

USA (1920-24)

USS Omaha, 9 others

The new kids on the block

The Omaha were the first American cruisers after a very long eclipse dating back to 1907 (the Chester). They were originally designed in 1919, originally to bring the squadrons of large-scale destroyers (Wickes and Clemson classes) from the end of the Great War. Like them, they had this typical flush-deck and four funnels. Almost scaled-up versions used as destroyer leaders. In addition their artillery was quite original, with an arrangement of two twin turrets and fore and aft barbettes, an unlikely mix that illustrated their transitional nature. They were launched in 1920-23 completed in 1922-24, bearing the names of southern American cities (Omaha, Milwaukee, Cincinnati, Raleigh, Detroit, Richmond, Concord, Trenton, Marblehead, and Memphis). Built lightly, they relied on speed and were part of this generation so-called “tin-clad cruisers”, relying on speed as their only protection at a time rangefinder still lacked precision for fast-moving targets. However they were somewhat heavy and particularly wet in heavy weather in the North Atlantic/ They quickly acquired such reputation that sailors used to joke that their machines did not run on oil but with Atlantic seawater. These cruisers had a long career, being modernized and spent all the inter-war on various stations and still be very active in world war two, the class avoiding a single loss in service.

Omaha class drawing, and an example of early 1942 camouflage

Genesis and design

The Omaha class was first envisioned in 1915 when it was clear that the US Atlantic Fleet lacked fast cruisers needed for scouting and at the same time deny enemy cruisers access to intelligence on the fleet or screen friendly forces. At that time, the Chesters were already 8 years old and were not enough in numbers compared to the massive battleships construction plans. The first specifications called for high speed (35 kn (65 km/h; 40 mph)) to lead and cooperate with destroyers, and having the firepower to over-match them as well. Oddly enough, UK was considered a possible (if very improbable) enemy on the Atlantic, and the team responsible for the design carefully studied the British Centaur, a subclass of the prolific C-class cruiser. When the final blueprints were approved in 1918, their resemblance with the Clemson class destroyers was considered a possible way to cheat the enemy, a bit like a “Q-ship”, to conceal its real firepower, and plans were even made to apply the very same camouflage patterns used on these destroyers, at larger scale.


In the end, these 7,000 tons ships sacrificed a lot to speed, and bear an armament spread between fore and aft standard turrets (the first for this caliber, but also adopted on the British Enterprise) the remainder eight of the twelve 6-inch/53 caliber guns being placed in casemates, four on each side located in upper and lower casemates. These 6-in guns were brand new, and first appeared on this class: The 6 inch x 53 caliber was equivalent to 8 meters and each gun side had swing Welin breech block and Smith-Asbury mechanism weighed. Each one was about 10 tonnes using silk bags containing 44-pounds (20 kg) of smokeless powder. They were loaded with 105-pound (47.6 kg) projectile and fired at 3000 feet per second (900 m/s) muzzle velocity. This traduced by a maximum range of about 21,000 yd (19,200 m) at 20 degrees elevation maximum. The barrels were built-up with a liner, tube, full-length jacket, and 2 hoops and its life expectancy was about 700 effective full charges (EFC) per liner. These guns were particular as being fitted in the new Mark 13 casemate mounting designed for the Omaha class, the primary battery also intended for the secondary battery of the never-completed Lexington-class battle cruisers and South Dakota-class battleships.

Secondary armament comprised two 3 in (76 mm)/50 caliber anti-aircraft guns. The standard Mark 3″/50 caliber guns (Marks 10, 17, 18, and 20) from 1915 were dual purpose, after initial Mk.2 going back to 1898 being anti-ship only, the low-angle Marks 3, 5, 6, and 19 were being mounted on small ships, auxiliaries and submarines. These guns were true “quick-firing”, using fixed ammunition with powder case and projectile permanently attached. The shells weighed 13 poundes, with an explosive bursting charge of 0.81 pounds in AA configuration or 1.27 pounds for High Capacity, explosive means. Maximum range was 14,600 yards °45 in elevation up to 29,800 feet (9,100 m) in ceiling at 85°. The barrel’s life expectancy was 4300 EFC. Rate of fire was 15–20 rounds per minute at a muzzle velocity of 2,700 ft/s (820 m/s).

There was also a set of ten torpedo tubes, spread into two triple and two twin 21 in (533 mm) torpedo tubes, with reloads. These could have been the recent Bliss-Leavitt Mark 8 torpedoes of 1911, surface models used on the Wickes Clemson classes and 1920s cruisers. Production of this model went on from 1913 to the interwar, many being still in service by WWII, epecially on PT-boats. Each weighted 2,600 pounds, was 256.3 inches (6.51 m) long for a diameter of 21 inches and a maximum firing range of 16,000 yards. They carried a warhead filled with TNT which weighted 466 pounds, expliding on contact. They were propelled by a turbine fed by a propellant combining Air (2800 psi, 23.4 cuft), water (90 US pints or 43 l) or Alcohol (49 US pints or 23 l) up to 36 knots (65.1 km/h). There were also rails, helped by the flush-decks, to carry up to 224 mines. However after a few years of service and tests with these, Secretary of the Navy, Curtis D. Wilbur after receiving reports orderered the rails to be removed from all cruisers. Later on, in 1933, the 3-inch AA guns were increased from two to eight while two lower torpedo tubes were removed and the openings welded shut. Still, for the same reasons in 1940, their lower aft 6-inch guns were removed and also plated over. In early 1942 they received also three quadruple 1.1-inch (28 mm)/75 gun mounts “Chicago Pianos”. Later they were removed and replaced by the standard Bofors 40mm guns while about fourteen single Oerlikons were installed.


Four shafts were connected to four Westinghouse reduction geared steam turbines, fed by 12 Yarrow boilers each working at 265 psi (1,830 kPa) for a total of 90,000 shp (67,000 kW). Top speed was 35 knots (65 km/h; 40 mph) with an endurance of 9,000 nmi (17,000 km; 10,000 mi) at 10 kn (19 km/h; 12 mph). However it was observed that sustained high-speed steaming can contaminate the oil tanks with sea water, because of leakages and the low freeboard causing water to be ingested through doors, vents, deck hatches, or torpedo and barbettes rear openings.


Poorly insulated, these cruisers were icy and wet in winter, but furnaces in summer under the tropics. Their anti-submarine protection was quite advanced however, but they lacked a full-length waterline armor belt. Their belt was 3 in (76 mm), the deck 1 1⁄2 in (38 mm), the conning Tower was ​1 1⁄2 in and bulkheads were ​1 1⁄2-3 in. In fact the boilers, engine rooms and steering gear were not better protected than in a destroyer, but compartimentalization compensated for that. Indeed if the drawbacks of the cruisers were recoignized, the ships featured for the first time improved ASW defence as the propulsion machinery was laid out on the unit system. This consisted in spreading alternating groups of boiler rooms and engine rooms. The goal was in case of a single torpedo hit, the flooding was kept limited and the ships can survive. Their great speed was a match for submarines anyway. In fact, the cruisers were never used in their intended scouting role, which was taken by aircraft carriers, and were relegated to fleet-screening role, with better efficiency thnan destroyers due to their larger range and heavy firepower.

USS Richmond on trials in 1923
USS Richmond on trials May 11, 1923

The class comprised:
Strictly speaking, these cruisers are not placed in the WW1 section because of the date they were laid down, in december 1918 for the first two. The last one was commissioned in 1925.
USS Omaha (CL-4) was built at Todd Dry Dock & Construction Co., Tacoma, Washington, launched 14 December 1920 and commissioned 24 February 1923

USS Milwaukee (CL-5) was built at Todd Dry Dock & Construction Co., Tacoma, Washington, launched 24 March 1922 and commissioned 20 June 1923

USS Cincinnati (CL-6) was built at Todd Dry Dock & Construction Co., Tacoma, Washington, launched 23 May 1921, commissioned 1 January 1924

USS Raleigh (CL-7) was from Bethlehem Shipbuilding Corporation, Fore River Shipyard, Quincy, Massachusetts, launched 25 October 1922, comm. 6 February 1924

USS Detroit (CL-8) was from Bethlehem Shipbuilding Corporation, Fore River Shipyard, Quincy, Massachusetts, launched 29 June 1922, comm. 31 July 1923

USS Richmond (CL-9) was built at William Cramp & Sons, Philadelphia, launched 29 September 1921 and commissioned 2 July 1923

USS Concord (CL-10) same yard, launched 15 December 1921, commissioned 3 November 1923

USS Trenton (CL-11) same yard, launched 16 April 1923, commissioned 19 April 1924

USS Marblehead (CL-12) same yard, launched 9 October 1923, commissioned 8 September 1924

USS Memphis (CL-13) same yard, launched 17 April 1924, commissioned 4 February 1925

The Omaha class in the interwar

After 1925, the Navy start to have an idea of these ships in service and was not pleased with them. Already in 1918, there was an alternative design, which was dropped but looked more promising: This new class and height 6-inch guns in four turrets forward and aft, and there was another lternative version intended to function as a monitor with two 14-inch guns in 2 single turrets. The other design was given four 8-inch guns in two twin turrets, but evolved later into the Pensacola-class cruiser.
These ten ships received in 1936 a new main telemeter, their front mast was reinforced, and a more modern AAA was added to them in 1939, consisting of several twin cal.50 (12.7 mm) machine gun mounts. In 1942, they were taken in hand for a reinforcement of their AAA, modernized notably with new 5-in (127 mm) guns and a very reinforced light armament (see specifications). Those sent to the Pacific as those assigned to the Atlantic served as escorts.

USS Marblehead, early 1930s
USS Marblehead, early 1930s

The Omaha in action during ww2

At min-1942 a radar was added to them, and what was left of torpedo tubes (four quadruple banks, originally 16 tubes) were removed to improve their stability, as well as catapults for float planes. In 1944, the Milwaukee was transferred to the USSR as a lend-lease becoming the Murmansk, to provide escorts from that port. None of these cruisers were sunk during the war. They were all scrapped in 1946, except the Murmansk, returned in 1947.

USS Omaha

After a career without surprise or notable event, in 1937 Omaha became grounded on a reef at Castle Island, Bahamas. After repairs at Norfolk Navy Yard, Portsmouth, Virginia, the ship sailed to Gibraltar on 30 March 1938, and served in the Mediterranean Sea until May 1939. The war broke up when she was undergoing extensive overhaul from 17 June until October 1939. She then operated in the Caribeans and was based in Lisbon to protect US citizens interests and relieve the ships which had done so after the Spanish civil war. She also sailed to Liberia, then was back to Pernambuco, Brazil, and the Carribeans, then Brooklyn for a refit. With two of ther sister-ships she began “neutrality patrols” between Brazil and Ascension Island. USS Omaha enforce the German blocus, by intercepting, boarding, and inspecting vessels as potential German merchants or hosting agents. She patrolled along South American lanes and afterwards searched for German blockade runners. In particular, she intercepted a seemilngly american freighter named Willmoto in November, 6, 1941, which revealed after inspection to be the German Odenwald, that her crew was prepared to scuttle.

When the Pearl Harbor attack erupted, she was to “execute WPL (war plan) 46 (Rainbow 5) against Japan.” but the Omaha did not joined the Pacific theater and went on with Atlantic patrols against U-boats, taking a deliberately more agressive stance and rescuing crews of many sunken ships in the area, Lammot Du Pont, and Charlbury (sunk by an Italian submarine), Harpagon, Rio Diamante, and several Brazilian merchantmen. On 30 April 1943,she collided with USS Milwaukee during manoeuvers at high speed, the latter hitting her starboard bow, and she was repaired in Rio de Janeiro for the at the Brazilian Navy Yard. She later rescued off the same coast the merchantman Rio Grande and sank the armed German blockade runner Burgenland and rescued the U-177 survivors. In July 1944 she was transferred to Malta, and in August participated in Operation Dragoon, the Provence landings, dealing with German shore batteries. In September she was back in southern atlantic, operated with the Brazilian Navy from then on, and in December seh underwent her last refit at the New York Navy Yard. She seached for survivors of the sunken Brazilian cruiser Baia, from Recife, on 8 July 1945. After the war ended she was decommissioned on 1 November 1945, striken and scrapped in 1946.

USS Milwaukee

(More to Come next)

USS Cincinatti with visitors Vancouver 1937
USS Cincinatti with visitors Vancouver 1937

USS Trenton on San Francisco Bay 11 August 1944
USS Trenton on San Francisco Bay 11 August 1944

USS Detroit at Puget Sound April 1944

USS cincinatti off NY City 22 March 1944
USS cincinatti off NY City 22 March 1944

Characteristics (in 1942):
Displacement: 7050 t, 8950 T FL
Dimensions: 172 x 16,2 x 7,25 m
Propulsion: 2 propellers, 2 Westinghouse turbines, 2 BW boilers, 70,000 hp, 32 knots max.
Armour: Maximum 90 mm belt, 25-50 mm blockhouse, bridges and reduced.
Armament: 10 guns of 152 mm (2×2, 6×1), 6 guns of 127 mm, 2×4 of 40 mm, 8 of 20 mm, 8 x 12.7 mm MG, 2×4 TT 533 mm.
Crew: 750

USS Milwaukee in june 1942, on her way to guadalcanal.

Sources/read More
ONI Drawings
Conway’s all the world fighting ships 1906-1921