B-class destroyer

The B class was a class of nine destroyers of the British Royal Navy, ordered as part of the 1928 Naval Estimates, launched in 1930 and that commissioned in 1931. The class was similar to the preceding A class, with minor modifications. They saw extensive service in the Second World War and five were sunk in combat; Blanche had the unfortunate distinction of being the first British destroyer lost during the war, when she was mined in the Thames Estuary some 2 months after the declaration of war.

Design
The main difference between the As and the Bs was that the latter dispensed with the minesweeping gear of the former in lieu of Asdic (sonar) and depth charges to suit them to anti-submarine work.

Unlike the A class the flotilla leader, Keith, was built upon the same hull as her sisters; the enlarged leader HMS Codrington of the A class proved to be tactically incompatible with her flotilla as she was both a number of knots faster and had a much greater tactical radius. As a result, Keith was too small to accommodate the entirety of Captain (D)'s staff, and Blanche was fitted as a divisional leader to carry the surplus.

Wartime modifications
The early losses likely had few modifications; restricted to replacing the after set of torpedo tubes with a QF 12 pounder anti-aircraft (A/A) gun - if at all. Like their contemporary older British destroyers, the B class were cascaded into convoy escort work as new vessels became available for fleet work. Modifications generally involved the aforementioned addition of the 12 pounder and striking the mainmast to improve the weapon's field of fire. 'Y' gun was landed to increase the space available for depth charge gear. The cumbersome metric wavelength Radar Type 286 was added to some ships as it became available. Based on the Royal Air Force's ASV set, and intended to warn against surfaced submarines, it had a fixed antenna that scanned in a forward arc, requiring the ship's heading to be changed in order to alter the search direction.

The 12 pounder gun was later removed from surviving ships, extra depth charges being carried in lieu. The 2 pounder guns were also replaced by QF 20 mm Oerlikon guns as they became available, with a further pair of the latter added in place of the searchlight position. Bulldog later received a further pair for a total of six Oerlikons. Beagle, Brilliant and Bulldog later received a much improved radar set in place of the rangefinder and director equipment; the centimetric wavelength Type 271 that combined the enormous advances of the cavity magnetron and the plan position indicator, resulting in a highly useful set that could detect a submarine periscope in the correct conditions. Bulldog and Beagle lost 'A' gun, gaining a Hedgehog ahead-throwing A/S weapon in its place. Bulldog received a QF 2 pounder Mk.VIII gun mounted as a bow chaser in 1944, to deal with the threat posed by German E boats.

Ships

 * Keith (H06), built by Vickers Armstrongs, Barrow in Furness, launched on 10 July 1930, sunk by Ju 87 "Stuka" dive-bombers off Dunkirk, France during Operation Dynamo on 1 June 1940.
 * Basilisk (H11), built by John Brown & Company, Clydebank, launched on 6 August 1930, sunk by Ju 87 dive-bombers off Dunkirk, France during Operation Dynamo on 1 June 1940.
 * Beagle (H30), built by John Brown, launched on 29 September 1930.
 * Blanche (H47), built by Hawthorn Leslie & Company, Hebburn, launched on 29 May 1930, sunk by a mine on 13 November 1939.
 * Boadicea (H65), built by Hawthorn Leslie, launched on 23 September 1930, sunk by air attack off Portland during Operation Overlord on 13 June 1944.
 * Boreas (H77), built by Palmers Shipbuilding and Iron Company, Jarrow, launched on 18 July 1930, loaned to Greece in 1944 and renamed Salamis.
 * Brazen (H80), built by Palmers, launched on 25 July 1930, sunk by air attack off Dover on 20 July 1940.
 * Brilliant (H84), built by Swan Hunter & Wigham Richardson, Wallsend, launched on 9 October 1930. Broken up in 1947
 * Bulldog (H91), built by Swan Hunter, launched on 6 December 1930. BU 1946