[11] The squadron's tasks during September 1939 consisted largely of exercising, included training Royal Navy surface ships in anti-submarine warfare.

The enemy submarine surfaced and an attempt was made to engage her with the deck gun, but this proved impossible due to the heavy seas.

[citation needed] Sealion conducted a number of patrols in late 1939 and early 1940, operating from Harwich, in the North Sea and off the Dutch coast.

Her first success came in the sinking of the German merchant ship August Leonhardt on 11 April 1940 off the Danish island of Anholt in the Skaggerak.

In subsequent patrols, Sealion made a number of unsuccessful attacks: on 6 May 1940 on the German transports Moltkefels and Neidenfels with six torpedoes; on 3 July 1940 on a convoy off the Boknafjord, Norway; and on 8 July 1940 on the beached wreck of the German merchant ship Palime off Obrestadt, which had struck a mine on 5 June 1940.

Crawford related that on one occasion Sealion was sent into the Skagerrak with the purpose of making her presence known so that the Germans would concentrate their anti-submarine efforts there[11] (possibly this was in April or June 1940[13]).

During the latter attack, Bryant failed to observe a tug (UJ 123[13]) which was escorting the convoy, which then rammed the Sealion, causing heavy damage to her periscopes.

Upon arrival at Swan & Hunter on 13 August, Crawford was relieved and sent to Dundee to join HMS L23 as first lieutenant, which sailed to Scapa Flow for anti-submarine exercises.

[11] On the way, Upholder participated in Operation Excess, acting as a screen for ships sailing to Malta, including HMS Illustrious, the Royal Navy's new aircraft carrier.

[11] From her base in Malta, Upholder engaged in normal patrolling duties with the purpose of preventing supplies reaching Axis forces in North Africa, with a particular focus on shipping sailing down the west coast of Sicily down the Tunisian coast to Tripoli and down the eastern side of Sicily from Taranto.

[11] On one occasion, on 12 April 1941, Upholder was out of torpedoes, but still achieved a minor success by persuading an enemy convoy to turn round by firing star-shell.

[11][14] On 26 April 1941, Upholder attacked the wreck of the German merchant ship Arta, which had run aground on the sand-banks off Kerkennah in Tunisia.

[11][14] On the following day, Upholder attempted to get close to the similarly grounded wreck of the Italian destroyer Lampo, but ran aground herself before she could reach her.

[11][14] Crawford later recalled that on one occasion Upholder was selected to land a party of commandos at Taormina in an attempt to assassinate Luftwaffe Generalfeldmarschall Albert Kesselring, who intelligence indicated was staying at the Miramar Hotel.

Crawford was on watch and saw a dark shape and called Wanklyn to the periscope, who took over and carried out a daring attack for which he was later awarded the Victoria Cross.

In July, Upholder encountered two Italian cruisers, Giuseppe Garibaldi and Raimondo Montecuccoli, steaming at about 22 knots and escorted by destroyers.

[19] Crawford found the U-boat's periscopes to be "superb", but noted that a great quantity of water would break over the bridge in even the slightest sea.

[20] Unfortunately, during training of watch divers in surfacing and diving the submarine, when diving after taking a sun-sight to find her position, the petty officer on watch pulled the wrong lever, which resulted in high-pressure air being blown into the "Q"-tank with both vent and Kingston valve shut, which damaged the tank and the battery, forcing Unseen to go to Sheerness for repairs to the tank before setting off for the Mediterranean.

The bleeding could not be stopped, and Unseen was forced to divert to Falmouth in order to obtain medical assistance at the local hospital.

[19][20] In November, she was sent to the waters off Toulon to observe French naval movements in the days leading up to the start of Operation Torch.

[19] At that time, or perhaps one or two days later (the sources are not clear), Unseen was forced hurriedly to dive to avoid a destroyer, but she had already been spotted by the enemy.

[19] To celebrate their escape, Crawford ordered a diving helmet to be sewn onto Unseen's Jolly Roger when they returned to Malta the following month.

[19][20] Due to the severe shortage of supplies in Malta, she sailed with a "dummy deck" underfoot throughout the submarine which was composed of provisions.

[20] As the "new boy", he and Unseen spent Christmas on patrol off North Africa between 21 and 30 December, attacking two convoys and firing seven torpedoes, but scoring no hits.

On 18 April, during a patrol off the north coast of Sicily, Unseen attacked and sank the German auxiliary submarine chaser UJ-2205.

[21][12] In late July and early August 1943 Unseen took part in further beach reconnaissance, this time off the east coast of Calabria.

[20] On 28 August, Unseen sank an Italian auxiliary patrol vessel, V216/Fabiola, off Vlorë, Albania, with a mixture of gunfire and scuttling charges.

[20] By firing a full salvo when the two target ships were overlapping, Crawford achieved the remarkable result of sinking both.

[25] Crawford was awarded the Distinguished Service Cross (DSC) on 2 September 1941, while First Lieutenant of Upholder, for "skill and enterprise in successful submarine patrols".

[21] Crawford was also mentioned in dispatches on 18 April 1944 for "gallantry, skill and devotion to duty in successful patrols in H.M. submarines", almost certainly in respect of his exploits in Unseen.