With funds gathered through a Naval Savings Campaign in 1942 known as Warship Week, the ship was adopted by the civil community of Ulster's County Down.
Ulster was one of eight U-class destroyers ordered as the 7th Emergency Flotilla on 12 June 1941. The U-class were War Emergency Programme destroyers, intended for general duties, including use as anti-submarine escort, and were to be suitable for mass-production. They were based on the hull and machinery of the pre-war J-class destroyers, but with a lighter armament (effectively whatever armament was available) in order to speed production. The U-class were almost identical to the S-class ordered as the 5th Emergency Flotilla and the R-class ordered as the 6th Emergency Flotilla earlier in the year, but were not fitted for operations in Arctic waters.
The U-class were 362inchesft9inchesin (ftin) long overall, 348inchesft0inchesin (ftin) at the waterline and 339inchesft6inchesin (ftin) between perpendiculars, with a beam of 35inchesft8inchesin (ftin) and a draught of 10inchesft0inchesin (ftin) mean and 14inchesft3inchesin (ftin) full load. Displacement was 1777LT standard and 2508LT full load. Two Admiralty 3-drum water-tube boilers supplied steam at 300psi and 630F to two sets of Parsons single-reduction geared steam turbines, which drove two propeller shafts. The machinery was rated at 40000shp giving a maximum speed of 36kn and 32kn at full load. 615 tons of oil were carried, giving a range of 4675nmi at 20kn.
The ship had a main gun armament of four 4.7 inch (120 mm) QF Mk. IX guns, capable of elevating to an angle of 55 degrees, giving a degree of anti-aircraft capability. The close-in anti-aircraft armament for the class was one Hazemayer stabilised twin mount for the Bofors 40 mm gun and four twin Oerlikon 20 mm cannons. Two quadruple mounts for 21 inch (533 mm) torpedoes were fitted (these were actually spare quintuple mounts with the centre tube removed), while the ship had a depth charge outfit of four depth charge mortars and two racks, with a total of 70 charges carried.
In June 1943 construction was completed and Ulster went into duty in the English Channel. By the end of the year she would be on duty in the Mediterranean and Adriatic on anti-submarine missions, receiving damage from return fire. In April 1944 the destroyer would return to home waters and towards the end of the year would refit and have new radar and advanced warning systems installed.[2]
At the beginning of 1945 Ulster was transferred to the British Pacific Fleet with the pendant "D", in keeping with the American system.[2]
Ulster, while serving with the British Pacific Fleet, had a near miss by a Japanese kamikaze and a 500 lb bomb during Operation Iceberg, the invasion of Okinawa. Ulster had her machinery spaces blown in and had to be lashed to the side of the Australian corvette HMAS "Kalgoorlie to prevent roll over to be taken to Leyte for temporary repairs, whence it sailed for Australia. Two sailors died and one was seriously injured in the attack the Kaloorlie conveyed the bodies and their burial party out to the deepest entrance to Leyte Gulf where the funeral was conducted. Nearly six months after the attack in October 1945 Ulster made it back to HM Dockyard, Chatham in England to undergo full repairs.[2]
After the Second World War Ulster was mostly used as a training vessel and for reserve purposes. Between 1953 and 1956 she underwent a full conversion to a Type 15 frigate at Chatham Dockyard. In 1957 she joined the 8th Frigate Squadron. Soon she was on duty in Iceland, Azores, and assigned to the North America and West Indies Station, based at the Royal Naval Dockyard in Bermuda, cruising to the West Indies and visiting the United States. In 1958 Ulster helped to restore power ashore in Nassau, Bahamas.[3]
In 1964 she was again put into reserve in Plymouth. A year later in 1965, Ulster was re-commissioned in the 2nd Frigate Squadron, but then in 1967 was withdrawn from operational service.
In 1966, whilst coming out of dry dock in Plymouth failure of her telegraphs meant Ulster having rung on full stern rammed the jetty. The heavily damaged stern was replaced with that of .[4]
During the late 1960s, Ulster was used by naval ratings from for seagoing training in the Sonar Control Room (SCR).In 1970 she was present at Portsmouth Navy Days; at the time she was the Navy's Navigational Training Ship.[5] The destroyer was used as a training hulk at between 1974 and 1980. Finally in 1980 Ulster was bought by Thos. W. Ward and broken up.[2]