During the remainder of December 1943 and until 19 January 1944, USS Colahan engaged in training exercises and Navy Yard overhaul at Pearl Harbor, and on the latter date sailed with Task Group 52.18 to engage in the capture and occupation of Kwajalein in the Marshall Islands. This Task Group was under the tactical command of Commodore Jarrett in USS Colahan, consisting of 8 LSTs (Landing Ship, Tanks), 6 LCIs (Landing Craft, Infantry), 3 SCs (Submarine Chasers), and 4 YMSs (Motor Mine Sweepers). The burden of defending the entire Task Group against enemy attack lay on the lone destroyer.
Shortly after midnight on 26 January, the USS Colahan made a sound contact with a submarine at about 2,400 yards and attacked with depth charges. Results were not observed nor was contact regained and the Task Group proceeded without further incident and made contact with Kwajalein 30 January. The next morning she was detached from Task Group to join Fire Support Group #3, screening the battleship USS Mississippi (BB 41) while she bombarded Enubju and Kwajalein.
During the early morning hours of 1 February 1944, USS Colahan was maneuvering in intermittent rain squalls to avoid collision with other ships and ran aground on a reef in South Passage. USS Colahan cleared the reef, but was unable to get underway due to extensive damage to both screws. USS Remey (DD 688) also ran aground and the battleship USS Washington (BB 56) rammed the battleship USS Indiana (BB 58) doing extensive damage to both ships.
USS Colahan was taken in tow by USS Thuban (AKA 19) on 8 February and arrived at Pearl Harbor on 19 February and remained in the yards undergoing necessary repairs until 12 May.
On 11 May, Commodore Jarrett shifted his flag to the USS Halsey Powell (DD 686).
Preparations were underway for the invasion of the Marianas Islands and the USS Halsey Powell would give fire support to troops on the Islands of Saipan and Tinian during the period 15 June until 9 August when she left for Guam, arriving on the 10th for Anti-Submarine duty until 16 August when she departed for Eniwetok Atoll, Marshall Islands.
On arrival at Eniwetok, USS Halsey Powell was attached to Task Group 38.2 and Commodore Jarrett was appointed Commander of Task Groups 38.8 with the THIRD FLEET (Adm. Halsey) and 58.8 when with the FIFTH FLEET (Adm. Spruance). Commodore Jarrett’s call letters were “OK-88.”
On 12 November 1944, Commodore Jarrett again shifted his flag to the designated flagship the USS Cushing (DD 797).
As a Screen Commander with the Fast Carrier Group, he took part in the action of Palau, in the Philippine Strikes, strikes in the South China Sea, Formosa, Iwo Jima, Okinawa, Tokyo and the Japanese Mainland. For “exceptionally meritorious service as Commander of Fire-Support Bombardment Unit, during the capture of the enemy Japanese-held Southern Marianas Islands from 14 June to 9 August 1944” he was awarded the Legion of Merit with Combat “V”. He received the Silver Star Medal “for conspicuous gallantry and intrepidity as Commander of Destroyer Squadron FIFTY THREE, during operations against enemy Japanese forces in Palau 9 to 14 September, Luzon 21-22 September and in the Ryukyu Islands and Formosa, 6–14 October 1944” and a Gold Star in lieu of Second Legion of Merit with Combat V for “exceptionally meritorious conduct” as Commanding Officer of Task Group 58.8 during operations against enemy Japanese forces in the Pacific Area from 18 March to 25 May 1945.
Task Group 58 or Task Group 38 when in Cruising Disposition, had 16 destroyers in a tight circle around cruisers, battleships and carriers of the Task Group. The eight Radar Picket destroyers were 50 miles out in the outer circle around the Task Group.
The concept of the Destroyer Radar Picket Line came about at a meeting on Feitabul Island that Admiral Halsey had with Les Woods, the Captain of the USS Laws (DD 558), Commodores Jarrett and Roland Smoot, both Squadron Commanders who had seen a great deal of action in the Pacific.
Commodore Jarrett was also awarded the Bronze Star Medal with Combat V for heroic service as Commander Scouting Line of Fast Carrier Task Forces during action against enemy Japanese forces in the vicinity of Okinawa, Nansei Shoto and Tokyo, Japan, from 10 February to 1 March 1945.
Commodore Jarrett continued his command of Task Groups 58.8 or 38.8 until 23 May 1945 when Captain W. J. Beecher took command of Desron 53. There was no formal changing of command and Commodore Jarrett made a surprise departure from the USS Cushing (DD 797). Before the Commodore’s Departure, his last message to all ships of his Squadron, DesRon 53 is as follows:
-T-A- SQUAD 53 2330255 D SQUAD 53 GR 16 BT
SORRY TO LEAVE A LOYAL FAMOUS SQUADRON X
BEST WISHES FOR CONTINUED SUCCESS X
UNCLE BEANY BT