HM S/M Unity

Unity shortly after trials
PennantN 66 
ModFirst Group 
Built byVickers Armstrong, Barrow-in-Furness
Ordered5 Nov 1936 
Laid down19 Feb 1937 
Launched16 Feb 1938 
Commissioned5 Oct 1938 

The U-class were initially designed as unarmed submarines for anti-submarine training [clockwork mice]. Armament was added to the design later, including two external torpedo tubes resulting in a pronounced snub bow. The ‘U’ class was a small patrol submarine with a bow salvo of six torpedoes but retaining the internal main ballast tanks and diesel-electric propulsion proposed for the unarmed training submarine.


191′ x 16.1′ x 14′ = 630 tons (surface)
730 tons (submerged)


Four 21″ internal bow torpedo tubes.
Two 21″ external bow torpedo tubes.
Ten 21″ Mark VIII torpedoes or eight 21″ Mark VIII torpedoes and a 3″ Mark III gun. Two Lewis guns and five rifles.


Diesel-electric with two generators of 615 HP = 11.9 knots (surface)
38 tons oil fuel = 3260 miles at full speed or 7200 miles at economical speed.

Main motors 825 HP = 10 knots (submerged)
Batteries, 224 cells of 97 tons = 1.8 hrs @ 8 knots


Single Hull type.
Diving depth 200 feet.


3 Officers and 24 men.

Detection Equipment

Two 30 foot periscopes, Search and Attack.
Type 129 ASDIC set.

Simplified layout of Group 1 ‘U’ class. Note somewhat clumsy bow arrangement. Source: Hezlitt

Messrs. Vickers of Barrow, builders of the first three ‘U’ class submarines. This is probably Ursula. Note the complete absence of torpedo tubes

Unity arrived at her war station in the South Harbour Blyth on 28 August 1939.

Patrol 1: Unity [Lt. J. Brown, aged 30] left  Blyth 31 Aug 1939, prior to the declaration of war, to  patrol Zone B deep inside the Helgoland Bight. German Mine-sweeping trawlers were sighted within the Bight, also Brummer [16:10 September 8]. On September 9/10 an attempt was made to ram Unity, believed to have been a German destroyer.

Unity returned to Blyth on September 13, 1939. Upon examination the engine frames were found to be cracked. The Boat was put into dock for repair.

Patrol 1, Zone B

From October 11 to October 14 the Boat was involved in engine trials post refit. On October 14 the Boat sailed to Rosyth.

Patrol 2: October 15 Unity left Rosyth for a patrol in Zone E, Horns Reef, Amrum/Bovbjerg Light sector

Patrol 2, Zone E

On October 27, 1939 the Boat returned to Rosyth

Patrol 3: November 5, 1939, Unity left Rosyth for a patrol in the Skaggerak, in Zone C2.

Patrol 3

The Boat returned to Blyth on November 29, 1939

Patrol 4: Nov 20, Unity left Blyth, ordered to ‘Proceed with dispatch’ to Horns Reef, Zone E in the Helgoland Bight.

Patrol 4 Zone E2

Admiralty intended to keep round the clock watch on this area. Unity returned to Blyth on December 2. On her return journey she was ordered to trail behind the damaged Triad heading back to Rosyth, lest any German warships attempt to surprise her.

Patrol 5: 13-15 December, Unity carried out abortive North Sea patrol

Patrol 6 Zones E and B

Patrol 6: December 21, Unity left to patrol Zone E and B.Ursula had recently returned with information regarding a probable swept channel between Helgoland and the charted position of the Vyl Lightship. This was of crucial importance to operations in zones E and B but Lt. Brown in common with Lt. Massy-Dawson of Seahorse was given no directive as to how to proceed through this channel. Brown opted to approach Helgoland well to the West. This decision saved both Boat and crew as Unity passed clear of the minefield, ‘Sperre ‘B’, Martha Eins‘ which would later sink Seahorse with all hands. Unity returned to Blyth on January 5.

Unity went into dock at Blyth on January 12, 1940 and returned to active service on January 21.

On February 2, Unity and H34 left Blyth in company on a working up exercise. The submarines joined convoy F/S 85 and sailed past Harwich to the South coast. By February 8, Unity had reached Blockhouse. On February 25, Unity left Blockhouse for Harwich. She reached Blyth on February 27.

Patrol 7: February 29, Unity left Blyth for a patrol off Josing Fjord in pursuit of Altmark. At 08:50 Unity reported Altmark left Josing Fjord escorted by two Norwegian destroyers.  They were close in land and well within territorial waters. By 10:30 the ship and her escorts had passed Lista Light. Unity withdrew to the West to surface and send a report. Owing to ice damage to the main aerial this was not passed until 12:30. At 14:00  Unity was ordered to patrol off Hantsholm, Denmark and intercept Altmark. Altmark was not sighted again. The patrol ended on March 11. This was ERA Rob Roy McCurrach’s first submarine patrol. He observed;

“We found her without any difficulty, heavily escorted. We ran out to sea to signal this news to the Admiralty. They in their turn told us to diesel through the night at full speed and intercept her as she entered her base. We did as asked but our top speed was too slow. Altmark had sought and gained, sanctuary before we stood a chance of hitting her with a couple of ‘fish’. Our TI remarked, ‘Pity we didn’t whack a couple of fish at her, then the lads up forward might have had a bit more room”

At night we rolled like an old sea-cow. Cups jumped out of their racks, overfilled buckets of gash tipped onto their sides, water cascaded down the conning tower, hastened by the draught of incoming air to the diesels, food sloshed over the electric oven producing eye-searing fumes which stung like tear gas. The look-outs came down from the bridge, cold, wet, dirty- and nearly blind. The human chain handling up the buckets of gash for ditching cursed and blasphemed as the revolting stuff dribbled down their upturned faces but finally it was done…”

Unity returned to Blyth on March 11.

Patrol 7 Zone A3 and Josing Fjord

Patrol 8: Unity left Blyth on March 24 for a patrol in the Skaggerak North of Zone J. March 25, Unity rescued survivors from Dutch trawler Protinus. [On March 20, HEIIIs of KG26 were out in the North Sea hunting for British auxiliary patrol trawlers. On Middle Rough Bank East of the Tyne they bombed a neutral Dutch trawler from Ijmuiden called Protinus, which was flying a large Dutch flag. One bomb exploded near the bridge killing the skipper and a deck hand but the remaining crew took to the lifeboat. The aircraft strafed them but nobody was hit. There was no food, no compass and very little water. On March 25 at 16:00 Unity sighted the lifeboat. Upon establishing this was not a trap, Unity approached the survivors. Two had perished and the eight survivors were in a bad way. Unity was ordered to leave patrol to land the fishermen. Unity was however delayed because of bad weather. On March 28 the Dutch sailors were transferred to the Rosyth Auxiliary Patrol trawler, Agate off May Island. Later that day Radio Hamburg announced that Protinus had been sunk by a British mine. Unity returned to Blyth on March 30.

The crew of Unity rescues the crew of Protinus and lands them at Rosyth

Lt. Brown wrote the following in an appendage to his patrol report:

“I wish to pay tribute to the extremely fine and unselfish spirit displayed by the sailors whom I have the honour to command in their dealings with the survivors of the Protinus. Not only did they cheerfully sacrifice their very limited sleeping accommodation to these men but all ratings gave up very considerable amount of their time, which especially during the foul weather experienced on the trip to base was extremely precious to them. Massaging the extremities of the survivors, fetching them water and generally administering to them, they did their best under trying circumstances. The fine example set by Lt. Low and PO Knott was undoubtedly responsible for this”

ERA Rob Roy McCurrach:

At night we rolled like an old sea-cow. Cups jumped out of their racks, overfilled buckets of gash tipped onto their sides, water cascaded down the conning tower, hastened by the draught of incoming air to the diesels, food sloshed over the electric oven producing eye-searing fumes which stung like tear gas. The look-outs came down from the bridge, cold, wet, dirty- and nearly blind. The human chain handling up the buckets of gash for ditching cursed and blasphemed as the revolting stuff dribbled down their upturned faces but finally it was done…”

Patrol 9: The Boat left Blyth on April 2 for a patrol off the NW coast of Denmark [Zone E2] and also the Skaggerak.

Patrol 9 Zone E2

On April 5, Unity attacked a surfaced U-boat in position 56°03’N, 06°35’E.:

’08:37 hours – In position 56°03’N, 06°35’E sighted a outward bound U-boat. There was a very rough sea and a heavy swell at the time, making depth keeping extremely difficult. The u-boat, which appeared to be of the 250 tons class, was first seen at a range of 3,000 yards. The four internal bow tubes were brought to the ready but the outer door of No. 4 tube could not be opened so it could not be fired.08:48 hours – Fired three torpedoes from 2,000 yards. Two torpedo explosions were heard one at 08:56 hours and one at 09:02 hours. HE of the target was still heard after the first explosion but owning to the state of the sea the target could not be seen. It was feared the attack was not successful’

Unity’s target was in fact U-2 [Kplt. Rosenbaum]. U-2 had sailed from Wilhelmshaven on April 4 to patrol off Egersund. Before noon on April 5 she was patrolling northwards through the route green swept channel when at the time of Unity‘s attack two separate explosions were heard and the boat was violently shaken.

On April 9

’16:00 hours – Unity surfaced for a sun sight in position 55°58’N, 06°33’E. [off Ringkobing] Upon surfacing a vessel was sighted hull down to the Northward. Dived and set a course to close. 16:50 hours – The vessel was now at only 1,000 yards range. [The vessel was identified as the 3,000 ton Casablanca. Brown had not yet received the message from VA (S) that German merchants in the Skaggerak could be sunk on sight. He would have preferred to search the ship according to the prize rules but at Unity was not fitted with a gun, the ship was unlikely to obey commands from Lt. Brown. Conditions at sea were glassy calm ] The Asdic operator reported that she had stopped her engines. Shortly afterwards two depth charges exploded close by. Unity now tried to get into an attack position as this vessel was now clearly hostile. The attempts however failed as the target kept bows on. 17:10 hours The attempts to get into a firing position were now abandoned and Unity retired slowly to the West.

17:24 hours – Speed was now increased. This was immediately followed by four depth charges. Boat maintained silent routine

17:26 hours – Four more depth charges were dropped.

17:28 hours – Six more depth charges were dropped. The enemy was heard to steam up and down.

17:55 hours – Three more depth charges were dropped.

18:40 hours – Two more depth charges were dropped. These were not very close. 1930 hours – Returned to periscope depth. Nothing in sight’

2312 ton German Q-ship, Oldenburg

[On April 4, Oldenburg (aka Schiff 35), the sister of German Q-ship Casablanca had sailed from Wilhelmshaven North up the Jutland pensinula. On April 8 she reported attacking a submarine contact, assisted by vessels VP403 and VP408 of the 4 Vorpost Flotille. The German ships failed to obtain a firm contact on the submarine which was able to escape with ease. It would therefore appear that Unity‘s patrol report contains incorrect information and that the encounter took place on April 8, rather than April 9. This was Oldenburg‘s first patrol with an inexperienced crew.

On April 17, Unity returned to Blyth but a strange fate was soon to overtake the Boat – see ‘The Last Dive of HM S/M Unity‘.

ADM 173/16243, ADM 199/2573, ADM 173/16302,
ADM 199/1814 Naval Historical Branch D/NHB/9/2/17P, Staff History Submarine Operations, Vol 1

© P Armstrong