At 08:17 on 21 June, she encountered her first victim, the 1,177 GRT Dutch steam merchant ship Berenice, outbound from Bordeaux, carrying 1,000 tons of manganese ore and 22 passengers.

At 13:51 she fired her sole remaining torpedo at the Dutch steam merchant vessel Amstelland about 380 nmi (700 km; 440 mi) southwest of Lands End.

Stockhausen claimed to have sunk his target, but despite being disabled Amstelland remained afloat for two days with a flooded Number 5 hold before being taken in tow by the rescue tug HMS Marauder.

[9] Departing Wilhelmshaven on 8 August 1940, U-65 proceeded into the North Sea and around the British Isles on her way to her new base at the recently captured Lorient, in France.

The aim of this Abwehr-sanctioned mission, titled Operation Dove ("Unternehmen Taube" in German), was sabotage following transport to Ireland.

No targets were sighted until 20:00 on 14 September, when convoy HX 70 was located about 180 nmi (330 km; 210 mi) off Barra Head (in Scotland).

As the ship developed a heavy list, the crew abandoned their vessel in one lifeboat and a gig, signalling a nearby trawler to pick them up.

The trawler, the Icelandic Þórólfur (English: Thorolf), landed the survivors at Fleetwood on England's west coast on 17 September.

[10][11] A second successful attack occurred on 17 September 1940, when the boat torpedoed the British steam merchant ship Treganna which had been travelling with convoy HX 71.

A single torpedo hit sent her to the bottom 78 nmi (144 km; 90 mi) northwest of Rockall in a matter of seconds; of her 37 crew, only four survived.

A full month at sea passed before the submarine spotted her first target, the 5,168 GRT British steam merchant vessel Kohinur; recently separated from convoy OB 235.

Initially, 68 of 85 men aboard survived, however many of them were killed a few hours later when U-65 sank her second victim of the patrol, the 7,614 GRT Norwegian motor tanker Havbør.

[14] British sailors on a raft from Kohinur had warned Havbør that a submarine was in the area, but boats were lowered to assist the 31 survivors anyhow.

[15][16] On 16 November, the submarine found her next mark in the 3,059 GRT British steam merchant ship Fabian about 350 nmi (650 km; 400 mi) west of Freetown.

The U-Boat surfaced and finished off the stricken freighter with five hits out of eight rounds from the deck gun and she sank with the loss of six men.

One man was lost, the remaining 35 crew members were picked up by the British cruiser HMS Devonshire and landed at Freetown a few days later (29 November).

A second torpedo hit on the starboard side just forward of the midship house about 20 minutes later, showering the surrounding water with debris, some of which barely missed the lifeboats.

[22] On 31 December, U-65 sighted the 8,532 GRT motor tanker British Zeal traveling on a non-evasive course at 10.5 knots east of the Cape Verde Islands.

A first coup de grâce missed, due to a malfunction, but a second struck the starboard side at the bulkhead between Numbers 3 and 4 tanks about 30 minutes after the first hit.

The darkness and adverse weather prevented use of the deck gun, but having observed the crew abandoning ship the submarine departed the area, assuming the tanker would sink.

Despite three flooded tanks, two large holes in the starboard side, and a deck torn open by the explosions the engine room was found to be intact.

At dawn the next day, the crew re-boarded the vessel a second time, raised steam and headed toward Bathurst at five knots.

A few hours later the British destroyer HMS Encounter arrived, offered assistance, and then left to search for the long-departed attacker.

At 22:07 a single torpedo from U-65 struck the British steam merchant ship Nalgora (6,579 GRT) about 350 nmi (650 km; 400 mi) north of the Cape Verde Islands.

Joachim Hoppe, she made for the North Atlantic where, on 28 April she was attacked and sunk by depth charges from the British destroyer HMS Douglas.