History
India
Name	Jumna
Namesake	Yamuna River
Ordered	8 September 1939
Builder	William Denny and Brothers
Laid down	20 February 1940
Launched	16 November 1940
Commissioned	13 May 1941
Decommissioned	31 December 1980
Fate	Broken up 1981
General characteristics
Class & type	Black Swan-classsloop
Displacement	1,250 tons original 1,350 tons modified
Length	299 ft 6 in (91.29 m)
Beam	37 ft 6 in (11.43 m) original 38 ft 6 in (11.73 m) modified
Draught	11 ft (3.4 m)
Propulsion	Geared turbines, 2 shafts: 3,600 hp (2,700 kW) (original) 4,300 hp (3,200 kW) (3.21 MW) (modified)
Speed	19 knots (35 km/h) (original) 20 knots (37 km/h) (modified)
Range	7,500 nmi (13,900 km) at 12 kn (22 km/h)
Complement	180 (original) 192 (modified)
Armament	6 ×QF 4 in (102 mm) Mk XVI AA guns (3 × 2) 4 ×2-pounder AA pom-pom 4 ×0.5-inch (12.7 mm) AA machine guns (original) 12 ×20 mm Oerlikon AA (6 × 2) (modified)

HMISJumna (U21) was aBlack Swan-classsloop, which served in theRoyal Indian Navy (RIN) duringWorld War II.

After India became a republic on 26 January 1950, the vessel was renamed as theIndian Navy'sINSJamuna.

HMISJumna was ordered in 1939, and built byWilliam Denny and Brothers. She wascommissioned in 1941,^[1] and withWorld War II underway, was immediately deployed as a convoy escort.Jumna served as an anti-aircraft escort during theJava Sea campaign in early 1942, and was involved in intensive anti-aircraft action against attacking Japanese twin-engined level bombers and dive bombers, claiming five aircraft downed from 24 to 28 February 1942:
"Chief Ordnance Artificer, Peter Cajetan Mascarenhas was awarded the Distinguished Service Medal for his part in defending the convoy against the Japanese aircraft which attacked it in the Sunda Strait. The citation in the London Gazette said that he had carried out repairs to guns during dive-bombing and machine-gun attacks, and had shown great devotion to duty. Leading Seaman Khan Mohammed, who displayed skill and initiative in engaging the Japanese with an Oerlikon gun was also awarded the Distinguished Service Medal. The Gunnery Officer, Lieut. A.J.V. LeCocq, R.I.N.V.R., was decorated with the Distinguished Service Cross and six of the Jumna's ratings were mentioned in Despatches, having shown "devotion to duty during heavy and continuous dive-bombing attacks".^[2]

On 12 February 1944, TheJapanese submarine Ro-110 was depth charged and sunk east-south-east offVisakhapatnam, India by the Indian sloopJumna and the AustralianminesweepersHMAS Launceston andHMAS Ipswich.Ro-110 had attacked convoy JC 36 (Colombo-Calcutta) and torpedoed and damaged the British merchantAsphalion (6274 GRT).^[3]

In early January 1945, she was deployed withHMIS Narbada to support the landing of the 74th Indian Brigade of theBritish Indian Army on theAkyab Peninsula, as a part of Operation Lightning.Jumna andNarbada engaged Japanese batteries up theKaladan River nearPonnagyun. After embarking troops, she joined Task Force 64 headed byHMS Phoebe for support of landing by 3rd British Commando Brigade between Akyab andRamree with the destroyerHMAS Napier and HMISNarbada.

Following Indian independence, she was allotted to India, becomingINSJamuna in 1950 when India became a republic. She was later converted to asurvey vessel and was decommissioned on 31 December 1980.^[4]

• Collins, D.J.E. (1964).The Royal Indian Navy, 1939 - 1945. Combined Inter-Services Historical Section (India & Pakistan).
• Hague, Arnold (1993).Sloops: A History of the 71 Sloops Built in Britain and Australia for the British, Australian and Indian Navies 1926–1946. Kendal, England: World Ship Society.ISBN 0-905617-67-3.

• Black Swan-class sloops of the Royal Indian Navy
• 1940 ships

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