The Beagle class were coal-fuelled ships, designed for a speed of 27 kn (31 mph; 50 km/h) and armed with a 4 in (102 mm) gun and two torpedo tubes.

While participating in the Gallipoli campaign, the destroyer rescued the crew of the French battleship Bouvet, sunk by a naval mine.

[1][2] The vessels were coal-burning after concerns had been raised about the availability of fuel oil in time of war and the bridge was larger and higher than previous designs.

[12] Up to 226 long tons (230 t) of coal was carried, giving a design range of 2,000 nautical miles (3,700 km; 2,300 mi) at 15 knots (28 km/h; 17 mph).

[10][12] Mosquito was laid down at Fairfield Shipbuilding and Engineering Company's Govan shipyard on 22 April 1909, was launched on 27 January the following year and completed on 11 August.

[26] The ship escorted the ex-Union-Castle Line troopship Grantully Castle carrying the Suffolk Regiment from Port Sudan to Suez on 9 October.

On the night of 1/2 March, along with Basilisk, Grasshopper and Racoon, the destroyer escorted trawlers attempting to clear the minefields across the narrows of the Dardanelles straits.

[29] On the night of the 18/19 March, the destroyer was involved in another attempt to clear the mines, this time escorting three trawlers and two picket boats.

Even more consequentially, the battleships Bouvet, Ocean and Irresistible hit mines and sank, the destroyer rescuing the majority of the survivors from Bourvet.

[39] On 5 February 1918, Mosquito was part of the escort for Convoy HX 20, bound from Halifax, Nova Scotia, to Liverpool when the troopship Tuscania was torpedoed by the German submarine UB-77 south west of Islay.

As the force returned to a peacetime level of strength, both the number of ships and personnel needed to be reduced to save money.