The British laid the groundwork for several major components of modern warfare during World War 1 (1914-1918) - namely the "tank" (then called a "landship" )and the aircraft carrier. For the latter, experimentation into launching and accepting aircraft culminated with HMS Argus (I49) in 1918. She was acquired (prior to the war as she underwent construction as a passenger ocean line) and suitably modified with a full-length flight deck. This arrangement then set the standard for carrier designs heading into the 1920s. The vessel proved vital in trialing various components of carrier operations including arrestor gear and fleet doctrine involving carrier ship types operating in conjunction with conventional warships such as destroyers and corvettes.
With the success found through Argus, the British Royal Navy looked to perfect the carrier through a purpose-built type so a keel was laid on January 15th, 1918 for a new vessel - to be named HMS Hermes (95) - and the hull was launched on September 11th, 1919. Too late for service in World War 1, HMS Hermes was nonetheless made ready for the threats of the next decade. Her builder was Armstrong Whitworth.
While Hermes marked the first true "purpose-designed" aircraft carrier anywhere in the world she was not officially commissioned until February 18th, 1924. This left IJN Hosho of the Imperial Japanese Navy to be commissioned into formal service sooner when brought online in 1922. Herme's slow road to operational service was hindered by the end of World War 1 itself in November of 1918 - giving the new warship less priority than she would have had at the height of the war.
To expedite her construction, HMS Hermes mimicked the form a cruiser warship so one of her early criticisms became her size which limited how many aircraft the vessel could embark. A main deck was set over the hull and formed a bulk of her strength. A 400-foot hangar area was added atop this structure and, above this, came the flight deck. The island superstructure, containing her bridge and other key components of a warship (including her mast), was seated atop this. The whole island superstructure was set to starboard, a design feature proven by the dimensionally larger HMS Eagle. Her standard operating crew numbered 566 (sans the air crew) and armor protection ranged from 3" at her belt to 1" along the deck. Overall dimensions induced a running length of 600 feet, a beam of 70.2 feet and a draught of 23.2 feet.
Hermes displaced 11,000 tons (standard) and up to 14,000 tons under load. Her propulsion system consisted of 6 x water-tube boiler units feeding 2 x geared steam turbines driving 2 x shafts at 40,000 shaft horsepower. She could make headway in ideal conditions at 25 knots and range out to 6,400 miles.
Since Hermes was not a true warship per se, her armament suite suited her intended battlefield role - mainly defensive in nature as her aircraft were to provide the offensive arm and support would be from accompanying surface ships surrounding the valuable vessel. As such, she carried weaponry in the form of 6 x 5.5" main guns that offered a light measure against attacking surface ships and 4 x 4" Anti-Aircraft (AA) guns for point defense against incoming aerial threats. As designed, HMS Hermes held a limited aircraft-carrying capability - typically numbering 12 fighters. A maximum of 20 could be carried if pressed.
HMS Hermes' ocean-going career during the 1920s and 1930s were rather low key and she was reclassified as a training platform on July 16th, 1938. It wasn't until the lead-up to World War 2 (1939-1945) that her value was increased exponentially as she was given a refit in August of 1939 just one month prior to the German invasion of Poland (on September 1st). With that she was then recommissioned for service and given a dozen Fairey Swordfish torpedo bomber biplanes for her onboard inventory later that month. With the war in full swing for September 1939, Hermes used her aircraft to seek out and destroy German submarine threats.
As an interesting aside, the merchant vessel SS Mamari III was heavily modified as a decoy of HMS Hermes to help confuse enemy spotters as to the true operating location of the British vessel. This warship's career itself ended in June of 1941 when she was sunk by raiding German aircraft at Cromer, Norfolk.
From the first shots of the war in September 1939, HMS Hermes partook in various actions serving the Allies and Royal Navy. She blockaded enemy ports, engaged enemy shipping when possible and hunted submarines threatening Allied shipping. She was also used to support land-based forces offshore by way of her air arm. Her career ended against the Japanese at Ceylon on April 9th, 1942 when IJN carriers attacked with fighters and dive bombers - her sinking taking 307 of her crew with her. The Australian destroyer HMAS Vampire was also lost in the attack.