Six additional ships being built for the Brazilian Navy when World War II began in 1939 were purchased by the British and named the Havant class.

Most ships were recalled home or were sent to the North Atlantic from October–November 1939, after it became clear that Fascist Italy was not going to intervene in World War II.

Most of the H-class ships were sent to the Mediterranean in May in case Mussolini decided to attack France and the majority of the surviving Gs were sent to Force H at Gibraltar in July.

The G- and H-class ships of the Mediterranean Fleet escorted numerous Malta convoys, participated in the Battle of Cape Matapan in March 1941 and covered the evacuation of troops from Greece and Crete from May–June, losing two to German bombers and another so badly damaged that she was later written off.

These ships were based on the preceding F class, but the elimination of cruising turbines and the development of more compact machinery allowed their dimensions and displacement to be slightly reduced.

The destroyers carried a maximum of 450–475 long tons (457–483 t) of fuel oil that gave them a range of 5,500 nautical miles (10,200 km; 6,300 mi) at 15 knots (28 km/h; 17 mph).

[2] All of the ships had the same main armament, four quick-firing (QF) 4.7-inch (120 mm) Mark IX guns in single mounts, designated 'A', 'B', 'X', and 'Y' from front to rear.

For anti-aircraft (AA) defence, they had two quadruple mounts for the QF 0.5-inch Vickers Mk III machine gun on platforms between the funnels.

This was necessary as Hereward was fitted with a prototype twin-gun mounting that had a trunnion height 13 inches (33.0 cm) higher than the previous weapons, therefore it was necessary to raise the wheelhouse to allow the helmsman to see over the top.

Raising the wheelhouse meant it had to be placed in front of, rather than underneath, the bridge, and it was given angled sides, resulting in a characteristic wedge shape with a sloping roof.

Four to eight QF 20 mm Oerlikon cannons were added to the surviving ships, usually replacing the .50-calibre machine gun mounts between the funnels.

All of the survivors, except Garland, had 'A' or 'B' gun replaced by a Hedgehog anti-submarine spigot mortar, and their director-control tower and rangefinder above the bridge removed in exchange for a Type 271 target-indication radar.

[12] Their turbines were 2,000 shp (1,500 kW) more powerful than the private ships, which made them 0.5 knots (0.93 km/h; 0.58 mph) faster; their propulsion machinery was otherwise identical.

Wartime modifications were similar to the other G- and H-class ships as a 12-pounder AA gun replaced the aft torpedo tubes, 20 mm Oerlikons were added on the bridge wings and a Type 286 radar was installed.

The Brazilians decided to produce indigenous destroyers, the Acre class, at the Ilha das Cobras shipyard, Rio de Janeiro.

[38] Two ships, modified versions of the G class, were built for the Greek Royal Hellenic Navy (RHN) by Yarrow in the late 1930s.

With the exception of Garland which was under repair at Malta after a premature explosion of her depth charges, they returned home in October–November after it became clear that the Italians would not enter the war.

Hardy and the H-class ships were assigned to the 2nd Destroyer Flotilla and joined the Gs in the Mediterranean after commissioning for similar duties.

Unlike the 1st DF, the Second was transferred to Force K in Freetown in West Africa, to help search for German commerce raiders.

The German invasion of Norway caused Havant, Hesperus, and Havelock to be detached to reinforce the Home Fleet during the Norwegian Campaign.

[42] Garland, Grafton, Gallant, Hasty and Hereward were either under repair or refitting during the early stages of the Norwegian Campaign and did not participate in the Battles of Narvik in April.

[44] Garland was loaned to the Polish Navy in May after her repairs were finished and she remained in the Mediterranean, escorting convoys between Malta and Alexandria, Egypt, until she was transferred to the Western Approaches Command in September.

[4] Hotspur was assigned to the 13th Destroyer Flotilla, supporting Force H at Gibraltar in July; she was joined by Gallant, Greyhound, and Griffin shortly afterwards.

Gallant, Greyhound, Griffin, now assigned to the 14th Destroyer Flotilla of the Mediterranean Fleet, together with Hero and Hereward, participated in the inconclusive Battle of Cape Spartivento on 27 November.

Repairs were estimated to take until June 1942, but she was declared a constructive total loss and stripped of equipment after she had to be beached during an aerial attack on 5 April 1942.

[53] Greyhound was sunk by German dive bombers two months later, on 22 May, off Crete;[52] Hereward suffered a similar fate a week later.

[60] Whilst in transit, she ran aground off the Tunisian coast during the night of 5/6 April due to a navigational error and had to be destroyed to prevent her capture.

[62] To reinforce the escorts for Operation Vigorous, a convoy from Alexandria to Malta in June, Griffin and Hotspur were temporarily recalled to join their sisters.

[64] While escorting Convoy HX 228, Harvester rammed U-444 on 10 March, but was disabled in the process, so the French corvette Aconit finished off the submarine.

Garland transported food and other supplies to Dutch and Belgian towns immediately after the end of the war and was part of the Home Fleet until she was reduced to reserve in August 1946.