HMS Hercules was the second and last of the two Colossus-class dreadnought battleships built for the Royal Navy at the end of the first decade of the 20th century.

Aside from participating in the Battle of Jutland in May 1916 and the inconclusive action of 19 August, her service during World War I generally consisted of routine patrols and training in the North Sea.

The design of the Colossus class was derived from that of the earlier HMS Neptune with redistributed armour and more powerful torpedoes.

The turbines were rated at 25,000 shp (19,000 kW) and were intended to give the ship a maximum speed of 21 knots (39 km/h; 24 mph).

[2] During her full-power, eight-hour sea trials on 2–3 March 1911, she reached a top speed of 21.6 knots (40.0 km/h; 24.9 mph) from 28,922 shp (21,567 kW) in a moderate storm.

The Colossus-class ships carried enough coal and fuel oil to give them a range of 6,680 nautical miles (12,370 km; 7,690 mi) at a cruising speed of 10 knots (19 km/h; 12 mph).

[2] They had a waterline belt of Krupp cemented armour that was 11 inches (279 mm) thick between the fore and aftmost barbettes that did not cover the full length of the ships.

Hercules recommissioned with a full crew on 31 July and was assigned as the flagship of the 2nd Division of the Home Fleet.

On 19 December Vice-Admiral Sir John Jellicoe assumed command of the division, which was renamed the 2nd Battle Squadron (BS) on 1 May 1912.

During this time, Vice-Admiral Sir George Warrender, Bt relieved Jellicoe as commander of the 2nd BS.

[15] Most of it was briefly based (22 October to 3 November) at Lough Swilly, Ireland, while the defences at Scapa were strengthened.

On the evening of 22 November 1914, the Grand Fleet conducted a fruitless sweep in the southern half of the North Sea; Hercules stood with the main body in support of Vice-Admiral David Beatty's 1st Battlecruiser Squadron.

[16] The 1st Battle Squadron cruised north-west of the Shetland Islands and conducted gunnery practice on 8–12 December.

[17] Jellicoe's ships, including Hercules, conducted gunnery drills on 10–13 January 1915 west of Orkney and Shetlands.

On the night of 25 March, Hercules and the rest of the fleet sailed from Scapa Flow to support Beatty's battlecruisers and other light forces raiding the German Zeppelin base at Tondern.

On 21 April, the Grand Fleet conducted a demonstration off Horns Reef to distract the Germans while the Imperial Russian Navy relaid its defensive minefields in the Baltic Sea.

The Royal Navy's Room 40 had intercepted and decrypted German radio traffic containing plans of the operation.

[22] On 31 May, Hercules, now under the command of Captain Lewis Clinton-Baker, was the twenty-third ship (or second from the rear) from the head of the battle line after deployment as part of the 6th Division of the 1st BS.

About five to ten minutes later, she engaged several German destroyer flotillas with a few salvos from her main armament without result.

[23] After the battle, the ship was transferred to the 4th BS and became the flagship of its commander, Vice-Admiral Sir Doveton Sturdee.

[26] They enforced strict wireless silence during the operation, which prevented Room 40 cryptanalysts from warning the new commander of the Grand Fleet, Admiral Beatty.

The British only learned of the operation after an accident aboard the battlecruiser SMS Moltke forced her to break radio silence to inform the German commander of her condition.