Destroyer leader (DL) was theUnited States Navy designation for largedestroyers from 9 February 1951 through the early years of theCold War. United States ships withhull classification symbol DL were officiallyfrigates from 1 January 1955[1] until 1975. The smaller destroyer leaders were reclassified as destroyers and the larger ascruisers by theUnited States Navy 1975 ship reclassification sodestroyer escorts could be reclassified as frigates (FF) in conformance with international usage of the term.
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By the end ofWorld War I the destroyers intended toscreen formations ofbattleships had evolved to adisplacement of approximately 1,100 tons armed with four 4-inch (10 cm) guns and six or moretorpedoes.[2]Italy had built threeMirabello-classesploratori (scout cruisers) approximately 70% larger than contemporary destroyers. TheWashington Naval Treaty encouraged theUnited Kingdom's satisfaction with its traditional fleet ofV and W-class destroyers and theUnited States' contentment with the similarWickes andClemson-class destroyers, while the signatories with smaller fleets explored alternative warship configurations between the classical definitions of destroyer and cruiser. Italy launched three moreLeone-classesploratori[3] andFrance responded with sixChacal-classcontre-torpilleur super destroyers.Japan launched the minimumlight cruiserYūbari followed by theFubuki-class "Special Type destroyers" (特型駆逐艦,Toku-gata Kuchikukan) with endurance to escort theKido Butai mobile force ofaircraft carriers over the wide reaches of thePacific.[4]
Germany built similarly enlargedZerstörer when it commenced naval rearmament.[5] With the exception of theTribal class and a fewflotilla leaders, most British and American destroyers built between the world wars were smaller than contemporaryAxis destroyers; but as the battleships for which the smaller destroyers had been designed as escorts faded into restricted roles in the combat experience ofWorld War II, United States destroyer displacement increased to2100 tons,2200 tons, and2400 tons to supportFast Carrier Task Force operations.[6]
As the United States Navy thinned its wartime fleet followingWorld War II, the smaller destroyers were discarded until only those over 2,000 tons remained in active service.[6] Naval architects had a few years to evaluate captured ships and combat experience before there was any need for more warships. With large inventories of destroyers and cruisers, new surface warship designs explored placing high-efficiencyboilers in hulls of intermediate size. The first destroyer leaderUSS Norfolk was authorized in 1948 and laid down in 1949 as an anti-submarine hunter-killer cruiser based on theAtlanta-classanti-aircraft cruiser, themselves originally conceived as destroyer leaders. She was designated EDL-1 while engaged in experimental work with new sensors and weapons systems including SQS-23sonar,Weapon Alpha,RUR-5 ASROC and automatic3 inch/70 Mark 26 guns.[1] She served entirely in theAtlantic except for a single deployment to theIndian Ocean and cruise around the world in 1968 shortly before she was retired from active service.[7] A sister ship was authorized, but not completed after experience with the prototype did not justify repetition of the design.[1]
The next design was for an unarmored cruiser of displacement similar to ItalianCapitani Romani-class cruisers to carry the new5 inch/54 caliber Mark 42 gun. Each of the fourMitscher-class ships received somewhat different experimental propulsion machinery powered by 1,200 pounds per square inch (82 atm) (8.3 MPa)Combustion Engineering forced-circulation boilers in DL-2 and DL-3; andFoster Wheeler boilers in DL-4 and DL-5. DL-2 and DL-3 hadGeneral Electric turbines while DL-4 and DL-5 hadWestinghouse turbines. All four ships began operations in the Atlantic. DL-3 and DL-5 were transferred to the Pacific in 1956. DL-3 made routine deployments to the western Pacific for as long as she remained in commission, but DL-5 was transferred back to the Atlantic in 1963 after making a few western Pacific deployments. DL-2 and DL-4 made routine deployments to theMediterranean Sea.[8] The ships were built with AN/SPS-6 air search radar, AN/SPS-8 height finding radar, AN/QHBa scanning sonar and AN/SQG-1 attack sonar. During their first refit in the mid-1950s the AN/SQG-1 and AN/QHBa were replaced by AN/SQS-4 sonar and the secondary open3 inch/50 caliber guns were replaced by3 inch/70 Mark 26 guns. Later refits removed the unsatisfactory 3 inch/70 guns andWeapon Alpha.
After experimental flight operations with theBell HUL-1 andKaman HTK-1 aboardMitscher in 1957,helicopter decks and hangars for theGyrodyne QH-50 DASH were installed where the aft 3-inch guns had been. DL-2 and DL-3 underwent major overhaul at thePhiladelphia Naval Shipyard beginning in 1966 including newFoster Wheeler boilers, AN/SQS-23 sonar, AN/SPS-37 air search radar,AN/SPS-48 height finding radar, and theTartar Guided Missile Fire Control System forRIM-24 Tartar missiles.[9] DL-4 and DL-5 had earlier received a new 70-foot bow section mounting theAN/SQS-26 sonar and spent the remainder of their service lives testing these prototypes until retirement, when their sisters emerged from overhaul at Philadelphia in 1968 for another decade of service as guided missile destroyers.[10]
A third class of destroyer leaders was designed after observing the performance of propulsion and weapons systems tested aboard theMitscher class. The first three ships were ordered with three 5 inch/54 caliber guns shortly after the name change to frigates. The next three were ordered with two 5 inch/54 guns forward, and aRIM-2 Terrier missile system aft, marking the transition toguided missile frigates (hull classification symbol DLG), intended to defend aircraft carriers against anti-shipcruise missiles. All ten ships were completed with a single 5 inch/54 gun forward, anASROC launcher where the B gun would have been, and the missile system aft; but the class was variously namedCoontz for the first ship to be ordered with a missile system, orFarragut for the lowest numbered ship to be completed in that configuration. ASROC and sonar gave the guided missile frigates an anti-submarine capability that most of the World War II cruiser conversions lacked. All werereclassified as guided missile destroyers in 1975.[11]
Two additional DLG classes and two similar nuclear-powered ships (DLGN) were completed by 1975 for a total of twenty additional guided missile frigates. These significantly larger ships were reclassified as guided missile cruisers (CG/CGN) in 1975.[39] By 1995 the former guided missile frigates were replaced by theTiconderoga-class cruisers andArleigh Burke-class destroyers.[40]
