The oldest class of light cruisers still in service with the US Navy at the time of the American entry into World War II was the ‘Omaha’ class of 10 ships. This had been planned in the aftermath of World War I as the first light cruiser class designed in the USA for more than 10 years. The light cruiser had fully proved its worth in World War I, and as the starting point for its new type the US Navy took the British ‘Danae’ and ‘Delhi’ classes as well as the German ‘Dresden’ class. These classes had a speed of 29 and 28.5 kt respectively for the British and German types, which had a main armament of six 6-in (152-mm) and seven 5.9-in (150-mm) guns respectively, so the US Navy decided that its new class should have a speed of 35 kt and an armament of eight 6-in (152-mm) guns on a displacement of 7,100 tons. The guns were in casemated mountings fore and aft, and included four guns that could bear on either beam: it was therefore decided to add four more 6-in (152-mm) guns in two twin turrets located fore and aft, although this meant an increase of 400 tons in displacement, a 9-in (0.23-m) increase in draught, a 1-kt decrease in speed, and the trimming of the belt to a length on each beam alongside the machinery spaces. It was then decided that the originally planned torpedo armament of two submerged tubes should be replaced by 10 tubes above the waterline, and that two catapults and aircraft should be added, so the further increase in weight resulted in the omission of the after 6-in (152-mm) casemated guns in half of the class for improved stability.
The ships were launched between 1920 and 1924, and during World War II were generally used in the South Atlantic and a few secondary actions in the Pacific as well as for the gunfire support role in a number of secondary amphibious landings. As completed, the ships had a full-load displacement of 9,150 tons, an armament of 12 or 10 6-in (152-mm) guns including four in twin turrets, eight 3-in (76-mm) anti-aircraft guns in single high-angle mountings and 10 21-in (533-mm) torpedo tubes, protection in the form of a 3-in (76-mm) belt and 1.5-in (38-mm) deck, and a speed of 33.5 kt on the 90,000 hp (67105 kW) delivered to four shafts by steam turbines.
With an arrangement of four tall funnels grouped in two pairs, the ‘Omaha’ class light cruisers were not visually attractive, but the same cannot be said of the ‘Brooklyn’ class that followed the last ‘Omaha’ class ships after an interval of more than 10 years. The spur for the development of this classic class was the Japanese ‘Mogami’ class of large light cruisers that began to appear in 1935 in response to Japan’s completion of its quota of 12 heavy cruisers permitted under the limitations of the Washington Naval Treaty. Japan’s answer to this limitation was the ‘Mogami’ class, which was planned as a light cruiser type able to offer heavy cruiser capabilities through the combination of a large hull and an armament of no fewer than 15 6.1-in (155-mm) guns in five centreline turrets (three forward, including one super-firing pair, and two aft in a super-firing pair). In the days before radar, when the maximum effective firing range was limited by visibility, the advantage in nocturnal and indifferent weather operations lay with the ships that could deliver the higher volume of aimed fire, and here the Japanese felt that the advantage would generally lie with the ‘Mogami’ class light cruisers even in engagements with heavy cruisers.
The Americans responded to the ‘Mogami’ class ships with a type of basically similar concept but greater displacement, thicker armour (to the same basic levels as the ‘Astoria’ class of heavy cruisers with the exception of a slightly thinner but longer belt) and shorter overall length: the hull was of the flush-decked type, and the main armament of 15 6-in (152-mm) guns was carried in five triple turrets arranged in the same manner as those of the Japanese ships with the exception that in the American ships it was ‘B’ rather than ‘C’ turret that was the super-firing unit of the forward trio. The nine units of the ‘Brooklyn’ class were launched between 1936 and 1938, and their details included a full-load displacement of some 12,700 tons, an armament of 15 6-in (152-mm) guns in five triple turrets, eight 5-in (127-mm) dual-purpose guns in eight single mountings or, in the case of the last two units, four twin turrets, and 16 1.1-in anti-aircraft guns in four quadruple mountings, protection in the form of a 5-in (127-mm) belt and 3-in (76-mm) deck, and a speed of 32.5 kt on the 100,000 hp (74560 kW) delivered to four shafts by steam turbines. Modifications that were effected to the ships of the ‘Brooklyn’ class during World War II included a strengthening of the anti-aircraft armament by 16 40-mm guns in four quadruple mountings and between 20 and 24 20-mm cannon in single mountings. The ‘Brooklyn’ class ships saw very extensive and successful service in World War II, in which only one of the vessels was lost, and in the early 1950s six of the ships were passed in pairs to three US allies in South America, where some of the ships survived in fully serviceable form until the end of the 20th century.
The ‘Atlanta’ class, which was the US Navy’s next class of light cruisers, was completely different from the ‘Brooklyn’ class and, indeed, from any other type of American light cruiser. This resulted from the fact that the ships of the ‘Atlanta’ class were intended for service as anti-aircraft and flotilla leader types, a role which indicated that their inspiration was the British ‘Dido’ class of anti-aircraft cruisers. Although the four ships of the ‘Atlanta’ class, launched in 1941, shared a commonality of role with the ships of the ‘Dido” class, they were wholly American in the way in which their role should be achieved. The class had the armament (including two banks of torpedo tubes) and speed required for co-operation with destroyer flotillas operating round the edges of a carrier task force, but was really too large for this role: wartime experience revealed that more success might have been achieved by a reduction in the number of main-calibre guns to allow the incorporation of more than just two high-angle directors, which limited each ship’s ability to the engagement of just two aircraft at any one time. As completed, the ships had a full-load displacement of 8,100 tons, an armament of 16 5-in (127-mm) dual-purpose guns in eight twin turrets, 12 or 16 1.1-in anti-aircraft guns in three or four quadruple mountings, eight 20-mm cannon in single mountings and eight 21-in (533-mm) torpedo tubes, protection in the form of a 3.5-in (89-mm) belt and 2-in (51-mm) deck, and a speed of 33 kt on the 75,000 hp (55920 kW) delivered to four shafts by steam turbines.
Next came the 27 light cruisers of the ‘Cleveland’ class, which was to have numbered 39 including three ships that were cancelled and nine that were converted into aircraft carriers. The ‘Cleveland’ class was an improved version of the ‘Brooklyn’ class with one 6-in (152-mm) triple turret sacrificed to make space for a much improved anti-aircraft armament. Launched between 1941 and 1944, the ships had a full-load displacement of 13,755 tons, an armament of 12 6-in (152-mm) guns in four triple turrets, 12 5-in (127-mm) dual-purpose guns in six twin turrets, between eight and 28 40-mm anti-aircraft guns in four twin to four quadruple and six twin mountings, and between 10 and 21 20-mm cannon in single mountings, protection in the form of a 5-in (127-mm) belt and 2-in (51-mm) deck, and a speed of 33 kt on the 100,000 hp (74560 kW) delivered to four shafts by steam turbines.
There followed the seven anti-aircraft light cruisers of the ‘Oakland’ class, which were completed in two groups of two ships launched between 1942 and 1944 as well as three ships launched between 1945 and 1946. The ‘Oakland’ class was a further development of the “Atlanta’ class with a full-load displacement of 8,200 tons, armour protection in the form of a 3.75-in (95-mm) belt and 2-in (51-mm) deck, and a speed of 33 kt on the 75,000 hp (55920 kW) delivered to four shafts by steam turbines. The two groups differed principally in their armament: the four ships of the first group had 12 5-in (127-mm) dual-purpose guns in six twin turrets, 16 40-mm anti-aircraft guns in eight twin mountings, 16 20-mm cannon in single mountings, and eight 21-in (533-mm) torpedo tubes; while the three ships of the second group had 12 5-in (127-mm) dual-purpose guns in six twin mountings, 32 40-mm anti-aircraft guns in six quadruple and four twin mountings and 20 20-mm cannon in single mountings.
Comprising only two out of a planned 13 ships, the ‘Fargo’ class was a further development of the ‘Cleveland’ class with modifications to improve the efficiency of their guns’ fire: these changes included a more compact superstructure and the two uptakes trunked into a single funnel to give the guns larger firing arcs. The details of the two ships, which were launched in 1945, included a full-load displacement of 13,755 tons, an armament of 12 6-in (152-mm) guns in four triple turrets, 12 5-in (127-mm) dual-purpose guns in six twin turrets, 28 40-mm anti-aircraft guns in six quadruple and two twin mountings, and 28 20-mm cannon in 14 twin mountings, protection in the form of a 5-in (127-mm) belt and 3-in (76-mm) deck, and a speed of 33 kt on the 100,000 hp (74560 kW) delivered to four shafts by steam turbines.
The last American light cruiser design created during World War II was the ‘Worcester’ class, of which only two out of a planned 10 units were completed only well after the end of the war. The design was in essence a development of the ‘Oakland’ class with 6-in (152-mm) guns in fully automatic twin turrets replacing 5-in (127-mm) guns in manually operated twin turrets, resulting in a longer hull and a larger displacement. The details of the class included a full-load displacement of 18,000 tons, an armament of 12 6-in (152-mm) dual-purpose guns in six twin turrets and 24 3-in (76-mm) dual-purpose guns in 11 twin and two single turrets, protection in the form of a 6-in (152-mm) belt and 3-in (76-mm) deck, and a speed of 32.75 kt on the 120,000 hp (89470 kW) delivered to four shafts by steam turbines.
The other two other naval powers involved in World War II on the Allied side were France and the USSR, neither of which played a major part in naval hostilities. The French cruiser force included the three light cruisers of the ‘Duguay Trouin’ class launched in 1923 and 1924 with a full-load displacement of 9,350 tons and a main armament of eight 6.1-in (155-mm) guns in four twin turrets, the two heavy cruisers of the ‘Duquesne’ class launched in 1925 and 1926 with a full-load displacement of 12,200 tons and a main armament of eight 8-in (203-mm) guns in four twin turrets, the four heavy cruisers of the ‘Suffren’ class launched between 1927 and 1930 with a full-load displacement of 12,780 tons and a main armament of eight 8-in (203-mm) guns in four twin turrets, the single but outstanding heavy cruiser of the ‘Algérie’ class launched in 1932 with a full-load displacement of 13,900 tons and a main armament of eight 8-in (203-mm) guns in four twin turrets, the single light cruiser of the ‘Emile Bertin’ class launched 1933 with a full-load displacement of 8,480 tons and a main armament of nine 6-in (152-mm) guns in three triple turrets, and the six excellent light cruisers of the ‘La Galissonnière’ class launched between 1933 and 1935 with a full-load displacement of 9,100 tons and a main armament of nine 6-in (152-mm) guns in three triple turrets.
The USSR operated a number of obsolete and obsolescent cruisers in the 1920s and 1930s, and the only truly modern type available in World War II was the ‘Kirov’ class, of which six were completed before and during the war with a full-load displacement of 11,500 tons and a main armament of nine 7.1-in (180-mm) guns in three triple turrets.