In November 1915 a proposal was approved to build an experimental battleship whose design was to embody current war experience. It was to take the armament, protection and machinery of the Queen Elizabeth in a hull of new design, incorporating shallow draught and improved underwater protection. The effects of the mine and torpedo had already been well demonstrated during the war, and the loss of the dreadnought Audacious to a mine twelve months earlier, together with that of no less than five pre-dreadnoughts (Majestic, Ocean, Formidable, Irresistible and Triumph) plus a number of cruisers to mine or torpedo no doubt entered the design staff's thinking. It had also been demonstrated that, under war conditions, the effectiveness of casemate-mounted secondary armament was at best questionable; at worst they reduced the ability of ships to remain afloat in extreme cases.
By the end of November a preliminary design had been submitted to the Board of Admiralty. This showed a ship with a length of 810 feet and a beam of 104 feet, reducing the draught to 26ft 3in, a considerable improvement over Queen Elizabeth. The speed was 26.5 knots, protection virtually as good as the Queen Elizabeth, with bulges providing the under-water protection. As had happened before, however, the great length was a matter of concern because of docking facilities. Revised designs reduced length and beam. There followed the inevitable discussions and compromises and by early 1916 six or more proposals were being seriously considered, ranging from 657ft to 810ft in length, 90ft to 104ft in beam and speeds from 22 to 27 knots. All had eight 15in as main armament and displaced between 26,250 tons and 31,000 tons. At this point, Admiral Jellicoe, CinC, Grand Fleet, intervened, claiming that there was no need for more battleships but that battlecruisers were badly needed in view of suspected German new construction. Accordingly, six battlecruiser designs were prepared in February 1916, ranging from 32,500 tons to 39,500 tons, armed with eight 15in or four to eight 18in guns. Protection was of course reduced in comparison with that of the battleships. One was chosen for further working, and two variants, differing in the secondary armament, were prepared. The approved version displaced 36,500 tons, with a length of 860 feet, but the shallow draught of the initial proposals had been compromised by the need for a battlecruiser's speed. The increased machinery weight that this entailed increased the draught because the length was at the limit for docking. The design was accepted on 7 April 1916 and orders for three ships were placed that same day. A fourth ship to be named Anson was placed in July. This design, armed with eight 15in in four twin turrets, with a secondary armament of sixteen 5.5in guns, had a protective scheme which included an 8in waterline belt, horizontal protection being limited to 1.5in for the most part, with some 2in areas. Armour represented 27.8 per cent of design displacement. The lead ship, Hood, was laid down to this design on 31 May 1916, the same day as the fateful Battle of Jutland during which three British battlecruisers blew up with colossal loss of life. This prompted the inevitable post-mortem and while matters were being clarified Hood was suspended. The conclusion was reached that the losses had been caused by cordite fires resulting from flash, and it was not considered that shells had actually penetrated the magazines. So when the design of the new ships was modified, most attention was applied to improving flash-tightness in turret trunks, handling rooms, magazines, etc., while horizontal protection, the main defence against long-range plunging shellfire, was not greatly augmented. By 4 August a modified design had been approved, in which the main belt had been increased in depth by 1ft 8in, the turret armour increased, barbettes selectively increased and improvements made to other aspects of the vertical protection. These added some 1,200 tons to the displacement. Later there was a proposal that the main armament be altered to twelve 15in in four triple turrets, which was approved and Hood was laid down again on 1 September 1916. Subsequently, more detailed analyses of the Jutland action led to demands for better horizontal armour and new designs were prepared yet again. These led to the final design receiving further modification so that final approval was not given until 30 August 1917.
The main belt armour was now 12in thick and 9.5ft deep (of which 4.5ft were below the waterline) and extended from 'A to 'Y' barbettes, a length of 562 feet. It was angled out at 12°. Forward it was continued in 6in then 5in, while aft it was 6in. Above the main belt was a 7in strake, 7 feet deep, and a 5in strake, 9 feet deep; below it was a shallow strake of 3in armour abreast the boiler rooms. Behind the armour the plating was 2in thick, which was carried down to the bottom plating in 1.5in to form the anti-torpedo bulkhead. Outboard of this was a buoyancy space and a large bulge for torpedo protection. The latter were about 10ft in depth and extended for the full length of the magazine and machinery spaces. End bulkheads were 4in or 5in thick. Barbette armour was 12in reducing to 5in or 6in between decks, with the front of A being 10in and the rear of 'B' having 12in in these areas. The conning tower had a maximum of 11in. Turret armour comprised 12in KC fronts with 11in sides and rears. Roofs were 5in. Horizontal protection finally comprised a forecastle deck of l.25-2in, upper deck 2in max. over the magazines, and the main armoured deck was 3in on the flat over the magazines and 2in on the slopes. Forward there was l-2in on the lower deck; 3in being applied to the lower deck aft over the steering gear. Final designed displacement rose to 42,670 tons standard, 46,680 tons deep load.
To achieve the designed speed of 31 knots, the installed power was 144,000shp with twenty-four oil-fired Yarrow small-tube boilers in four spaces, supplying a four-shaft Brown-Curtis single-reduction geared turbine layout. There were three engine rooms, the foremost driving the outer shafts, the middle engine room the port inner and the after engine room the starboard inner shafts. On trials at load displacement, Hood reached 32.07 knots on 42,200 tons with 151,280shp.
The main armament finally comprised the standard 15in BL Mk I in twin mountings Mk II, these having 30° elevation. It had been specified from the outset that casemate mountings would not be fitted nor would 6in calibre weapons be carried. The secondary guns were 5.5in BL Mk I in single shielded mountings CPII. This gun, of Coventry Ordnance Works design, originated in cruisers laid down for the Greek Navy but taken over by the Royal Navy in 1914. It fired an 821b projectile to a range of 17,700 yards at 30°. Only twelve of the sixteen guns specified in the design were mounted, the four aftermost having been deleted as compensation for the improved armour scheme. There were five guns on each beam in the waist on the forecastle deck and two on the forward end of the shelter deck. Four single 4in QF Mk V on HA mountings Mk III completed the gunnery department. These were at the after end of the shelter deck, one on each beam and two in tandem on the centre-line. There were four upper deck torpedo tubes for 21in torpedoes, two on each beam under the mainmast, the two pairs forward having been omitted to compensate for the improved protection. In addition, there were two submerged tubes, one on each beam forward of 'A' barbette.
Fire control was provided by a main director on the conning tower fitted with a 30ft range-finder and a second director on the foretop with a 15ft range-finder. The after control position had a 15ft range-finder hood, and each turret had a 30ft range-finder.
Construction of Hood proceeded relatively slowly; her sisters, Howe, Rodney and Anson, laid down in October and November 1916, were suspended on 9 March 1917 because shipyard labour was needed for more pressing tasks such as merchant ship and escort craft construction. The Armistice of November 1918 resulted in the cancellation of the suspended ships, leaving Hood as the largest warship in the world for many years.
In 1920-21 a number of minor alterations were made to her bridge and rig and two of the four searchlights between the funnels were removed, but they were replaced again in the autumn of 1923. In a refit from November 1925 to January 1926, her high-angle control was improved with a 15ft HA range-finder being fitted on the after superstructure. The two searchlights were again landed. In 1927 there was a debate as to the possibility of improving the ship's horizontal armour, but this came to nothing at the time and in fact she was never to be improved in this respect, despite the intention to take her in hand after Queen Elizabeth, because of the outbreak of war in 1939. Hood was given a refit at Portsmouth from the beginning of June 1929 to the end of May 1931, when two eight-barrelled 2pdr Mk V were fitted on the shelter deck abreast the funnels, an HACS Mk I added to the after searchlight platform, a catapult and crane fitted on the quarterdeck, the flying-off platform removed from 'X' turret and minor modifications made to the bridge structure. Internally, fuel stowage was increased by 720 tons to a total of 4,615 tons. The catapult was not a success and it and the crane were removed in the late spring of 1932. During a subsequent overhaul from March to May of that year, two 0.5in quadruple MGs were fitted abreast the conning tower on the signal platform. At Malta in November-December 1937 Hood received an eight-barrelled Mk VI 2pdr mounting on the after control position, the range-finder being displaced. Two single 4in Mk IV HA mountings were fitted amidships on the shelter deck and two quadruple 0.5in Mk III were fitted on the after superstructure. Internally, the after submerged tubes were removed. Some six months later she received a director for the after 2pdr, and the two shelter deck 5.5in guns were supplanted by two single 4in Mk IV HA mountings. During her next refit, at Portsmouth in the first half of 1939, the two single 4in HA amidships were landed and in their place four twin 4in HA Mk XIX were fitted, two on each beam. Four 44in searchlights were fitted, two abaft the after funnel and the other pair on the after superstructure. Two HACS Mk III directors were fitted at the after end of the signal deck, port and starboard. After an interruption for trials, the ship continued to refit in July when the remaining single 4in were landed, the two shelter deck 5.5in replaced and the searchlights and tower between the funnels removed. During April and May 1940 at Devonport all the 5.5in guns were landed and three more twin 4in Mk XIX added at the after end of the shelter deck, one on the centre-line and one on each beam. In addition, she received five 7in twenty-barrelled UP mountings Mk I, one on 'B' turret and two on each beam on the shelter deck. Finally, from mid January to 15 March 1941 Hood was fitted with radar Type 284 for the 15in guns. More elaborate plans to increase her deck protection and fit 5.25in DP guns and other equipment were thwarted by the outbreak of war.
Hood joined the Atlantic Fleet as Flag, Battlecruiser Squadron, on commissioning. In May 1920 she was ordered to Reval for operations against the Bolsheviks, but before she arrived a change of policy saw the operation called off and that summer she visited Sweden, Denmark and Norway in company with Tiger and nine destroyers. Until November 1923, when she hoisted the Flag of the Special Service Squadron, Hood made cruises to Brazil and the Caribbean. On 14 May 1923 she paid off after her first commission and recommissioned next day. In June and July she again visited Norway and Denmark. The Special Service Squadron was formed for the purpose of 'showing the flag' to the colonies and dominions of the empire. Accompanying Hood was the battlecruiser Repulse and the ships of the 1st Light Cruiser Squadron, Delhi, Dauntless, Danae and Dragon. This world cruise began on 27 November 1923, and the flagship finally returned to Plymouth on 29 September 1924, having sailed to Cape Town, then across the Indian Ocean via Ceylon to Malaya, on to Australia and New Zealand and then across the Pacific to Canada. The squadron then sailed south to the USA, passed through the Panama Canal, and called at Jamaica en route for Halifax and Quebec before returning across the Atlantic. During the cruise Hood steamed 40,000 miles and was visited by a quarter of a million people. After a refit at Devonport from October to December 1924, she joined the Atlantic Fleet where she remained until March 1932, recommissioning on 7 January 1926 and 27 August 1928, after which she became Flagship, Battlecruiser Squadron. In March 1932 this was redesignated Home Fleet and thereafter Hood continued to serve with that fleet. In January 1935 she was in collision with Renown off the coast of Spain and was under repair until May. She was present at the Spithead Review of July 1935. In September 1935 she was transferred with the Battlecruiser Squadron to Gibraltar as a result of the Abyssinia crisis, but remained with the Home Fleet. A year later, after a refit at Portsmouth beginning 23 June, she recommissioned for the Mediterranean Fleet on 8 September 1936, arriving at Malta on 20 October. During this period she took part in the Spanish Civil War patrols 1937-38 and visited many Mediterranean ports. In February 1939 the Battle-cruiser Squadron was ordered back to the Home Fleet and Hood was given a refit at Portsmouth from February to August 1939 so she was in home waters at the outbreak of war.
Her initial operation was a sortie with Renown to cover a sweep into the Skagerrak, returning to Scapa on 23 September. Other operations were concerned with German blockade runners or with sweeps to locate German warships in the North Sea and North Atlantic. Following the sinking of Rawalpindi by Scharnhorst and Gneisenau in November 1939, Hood was attached to an Anglo-French force under French command (Dunkerque - Flag). From December 1939 Hood covered troop convoys from Canada then in March went to Devonport for repairs, which lasted until 26 May. In June 1940 she joined Force H as Flag on its formation at Gibraltar. On 3 July she participated in the attack on the French Fleet at Oran, when she was slightly damaged by splinters from the gunfire of her former consort Dunkerque. In July she covered the delivery of fighters to Malta by Argus and in August participated in a raid against Cagliari before returning to the Home Fleet, arriving at Plymouth on the 8th and reaching Scapa on the 11th. She remained with the Home Fleet for the remainder of her career. In November 1940 she joined the hunt for Admiral Scheer after the sinking of Jervis Bay, patrolling off Brest and Lorient. From February to March 1941 she was under refit at Rosyth and on completion took part in the hunt for Scharnhorst and Gneisenau 21-28 March. From April she was based at Hvalfiord, Iceland. After Bismarck sailed on her first Atlantic sortie, Hood (Flag) was ordered to join the hunt and sailed from Scapa on 22 May, accompanied by Prince of Wales and six destroyers. On the morning of 24 May action was joined with Bismarck and the heavy cruiser Prinz Eugen and after a short engagement, the British Flagship was hit by one or more 15in shells and blew up, disappearing in about three minutes. There were only three survivors.