Editing Brooklyn-class cruiser (section)

== Design ==
The ''Brooklyn''-class design was a further refinement of the {{sclass|New Orleans|cruiser|0}} [[heavy cruiser]] that preceded it.<ref>Friedman pp. 155–156</ref> The desire for the ''Brooklyn''s arose from the [[London Naval Treaty]] of 1930, which limited the construction of heavy cruisers, i.e., ships carrying guns with [[caliber]]s between {{convert|6.1|and|8|in|0}}. Great Britain needed trade control cruisers and hoped that the treaty would limit nations to smaller cruisers with a {{convert|6000|to|8000|LT|adj=on|lk=on|0}} range that she could afford. Agreement to the London Treaty and the proceeding with the American [[light cruiser]] design can be focused to [[Admiral (United States)|Admiral]] [[William V. Pratt]], who overrode the vehement objections of the [[General Board of the United States Navy|General Board]].<ref>Friedman pp. 164–165</ref>

Under the treaty the US was allowed {{convert|180000|LT|0}} for 18 heavy cruisers and {{convert|143500|LT|0}}, with no limit on the number of ships, for light cruisers.<ref>Friedman p. 187</ref> The United States needed large cruisers to deal with the extreme ranges that operations in the [[Pacific Ocean]] required. Cruisers with {{convert|6|in|adj=on}} guns and {{convert|10000|LT|0}} were therefore desired.<ref>''US Navy Light Cruisers'' location 77</ref> The US Navy's experience with the {{sclass|Omaha|cruiser|4}} was not all that could be hoped for. Their light hull design caused a stressed hull and was very overweight. 

Design started in 1930, with the first four of the class ordered in 1933, and an additional three ships in 1934. Basic criteria had been that speed and range should match heavy cruisers, and when the Japanese {{sclass|Mogami|cruiser|4}} carrying fifteen 6-inch main guns appeared, the new US ships would match their weaponry. Various combinations of armor and power plants were tried in the efforts to stay below the Treaty 10,000 ton limit.<ref name="w24x">Whitley pp. 248–249</ref> Aviation facilities were moved to the [[stern]] of the ship from the [[amidships]] position of the ''New Orleans''-class cruisers.<ref name="Friedman, Norman p. 183">Friedman p. 183</ref><ref>Whitley p. 248</ref>

From 1942, the [[Bridge (nautical)|bridge]] structure was lowered and [[radar]] was fitted.

===''St. Louis'' subclass===
The last two ships of the class, {{USS|St. Louis|CL-49|2}} and {{USS|Helena|CL-50|2}}, were slightly modified versions of the design with new higher pressure boilers and a [[unit system of machinery]] that alternated boiler and engine rooms to prevent a ship from being immobilized by a single unlucky hit; this system would be used in all subsequent US cruisers. Additionally, [[anti-aircraft|AA]] armament was improved. They were the first US cruisers to be armed with twin [[5"/38 caliber gun|5-inch (127&nbsp;mm)/{{wbr}}38-caliber guns]]. They could be distinguished visually from the other ''Brooklyn''s by the placement of the after deckhouse, immediately abaft the second funnel, and by the twin 5-inch mounts.

=== Armament ===

The ''Brooklyn'' class was equipped with 15 [[6"/47 caliber gun|6-inch/{{wbr}}47 caliber Mark 16]] naval guns, developed from the [[6"/53 caliber gun|6-inch/{{wbr}}53 caliber Mark 8]] used on the ''Omaha''-class cruiser. The decision was reached as the gun could achieve up to ten rounds per minute rate of fire. This gave the class the ability to send up to 150 rounds a minute at its intended target. This allowed the cruiser to smother an enemy ship with fire. The turret arrangement was five turrets, each mounting three guns on a single sleeve, which did not allow the guns in a turret to move independently. The 6-inch guns were of a new design, the Mark 16, which could fire a {{convert|130|lb|adj=on|abbr=off}} [[armor-piercing shell]] (AP) up to {{convert|26100|yd|0}} with twice the penetrative power of the old gun. The ammunition was of the [[Shell (projectile)#Separate loading cased charge|semi-fixed type]].<ref>{{cite web |last= DiGuilian |first= Tony |date= 12 February 2021 |title= 6"/47 (15.2 cm) Mark 16 |website= NavWeaps.com |url= http://www.navweaps.com/Weapons/WNUS_6-47_mk16.php |access-date= 5 September 2021}}</ref> <!-- noted at rising from {{convert|3.5|to|5.5|in}} at {{convert|10000|yd|0}} and {{convert|2|in|0}} of deck armor at {{convert|20000|yd|0}}. (Not sure what is being said here, what does "rising from 3.5 to 5.5in at 10,000yds" refer to? Is it supposed to be penetration at the distance?)--> The impact of the shell changed the General Board's view on the usefulness of light cruisers in service.<ref>Friedman p. 194</ref>

As designed, the anti-aircraft weaponry specified eight [[5"/25 caliber gun|{{convert|5|in|adj=on|0}}/{{wbr}}25 caliber guns]] and eight [[M2 Browning|{{convert|.50|in|1}} caliber M2 Browning machine guns]]. The intention to mount [[1.1"/75 caliber gun|{{convert|1.1|in|adj=on}}/{{wbr}}75 caliber]] anti-aircraft guns was frustrated and the requirement was not fully met until 1943. The weapon as deployed was less than satisfactory with frequent jamming and weight being serious issues.<ref>Schreier, Konrad F. (1994). "The Chicago Piano". Naval History. United States Naval Institute. 8 (4): 44–46.</ref> Some of the class had 5-in/38 caliber guns installed versus the 5-in/25 guns.<ref>Stille p. 100</ref> There were varied mixes of [[Oerlikon 20 mm cannon|{{convert|20|mm|adj=on|sp=us}} Oerlikon cannons]] and [[Bofors 40 mm Automatic Gun L/60|{{convert|40|mm|adj=on|1|sp=us}} Bofors gun]] mountings actually installed during World War II, 28 40&nbsp;mm (4 × 4, 6 × 2) and twenty 20&nbsp;mm (10 × 2) being the most common.<ref name="w24x"/>

=== Fire control ===

The ''Brooklyn'' class was deployed with the Mark 34 director and later the Mark 3 radar. This would be upgraded to the Mark 8 and again to the Mark 13 radar. The secondary battery was controlled by the Mark 28 and upgraded to the [[Ship gun fire-control system#Mark 33 GFCS|Mark 33 fire control systems]]. The associated radars were the Mark 4 fire control radar and upgraded again to the Mark 12. Two anti-aircraft fire directors were fitted to each ship. A late World War II refit saw the [[Ship gun fire-control system#Mark 51 Fire Control System|Mk 51 director]] installed for the Bofors guns. Night engagements were improved when in 1945, the Mark 57 and 63 directors were installed.<ref>Stille p. 130</ref>