First patrol

The boat's first patrol began with her departure from Kiel on 17 February 1941. Her route took her across the North Sea and through the gap between Iceland and the Faroe Islands.

She sank three ships on the 24th; Mansepool, Jonathon Holt, both southwest of the Faroe Islands and British Gunner 273 nautical miles (506 km; 314 mi) northwest of Cape Wrath (northern Scotland). Among those lost in the sinking of the Jonathon Holt was the travel writer Robert Byron.^[3] The Flower-class corvette HMS Petunia had ordered the crew of British Gunner to abandon their vessel even though the master had said the ship could be towed to safety.

The U-boat then damaged G.C. Brøvig. The Norwegian tanker was a victim of U-97's third attack on Convoy OB 289. The torpedo strike caused her to lose her bow, but the bulkhead held and the engines remained usable. With assistance from HMS Petunia, she arrived at Stornoway (in the Outer Hebrides),^[4] on 27 February. She was subsequently repaired and returned to service.

The patrol was somewhat marred when a crew-member was lost overboard on 3 March. The submarine docked at Lorient in occupied France on 7 March.

Second patrol

U-97 sank three more ships between Cape Farewell (Greenland)^[5] and southern Ireland in March and April 1941. They were: Chama and Hørda (on 23 and 24 March respectively) and Conus on 4 April. There were no survivors from Hørda or Conus.

Third and fourth patrols

The boat sank HMS Camito, an Elders & Fyffes banana boat that had been requisitioned as an Ocean Boarding Vessel and Sangro, west southwest of Cape Clear (southern Ireland)^[6] on 6 May 1941. On 8 May she struck again, sinking Ramillies southeast of Cape Farewell.

Sortie number four was relatively uneventful, starting from St. Nazaire on 2 July 1941 and terminating in the same port on 8 August.

Fifth patrol

Departing St. Nazaire on 20 September 1941, U-97 went south, slipped past the heavily guarded British base at Gibraltar and into the Mediterranean. She sank Pass of Balmaha 50 nmi (93 km; 58 mi) west of Alexandria on 17 October. The merchant ship had been part of the fourth convoy of Operation Cultivate, the relief of Tobruk. She also sank Samos on the same day.

An accident which left the IIWO (second watch officer) badly injured on 24 October forced the boat to cut her patrol short. She arrived at Salamis in Greece on the 27th.

Sixth and seventh patrols

Human frailties also came to the fore during the boat's sixth patrol when, having crossed the Aegean Sea towards Turkey, she was obliged by a sick crew-member, on 7 January 1942, to return to Salamis on the ninth.

The submarine's seventh patrol started and finished in Salamis.

Eighth and ninth patrols

Having moved to La Spezia in northwest Italy in February, U-97 was attacked by a Sunderland flying boat of No. 230 Squadron RAF off the North African coast. The aircraft dropped five bombs on the boat, but caused no damage.

Patrol number nine continued the shuttle-sequence between Salamis and La Spezia.

Tenth patrol

The situation improved for the crew when they sank Zealand and Memos 14 nmi (26 km; 16 mi) southwest of Haifa on 28 June 1942. The Marilyese Moller went to the bottom on 1 July about 27 nmi (50 km; 31 mi) west of Rafah^[7] in Palestine. The armed trawler HMS Burra reacted with three depth charges, but was unsuccessful.

11th and 12th patrols

These patrols began in Salamis and La Spezia; the latter finished in Pola (now Pula) in Croatia in May 1943.

13th patrol and loss

U-97's final patrol started with her departure from Pola on 5 June 1943. She sank Palima 30 nmi (56 km; 35 mi) south southwest of Beirut on the 12th. She was also successful against Athelmonarch northwest of Jaffa on the 15th.

The U-boat was sunk by a Lockheed Hudson of 459 Squadron, Royal Australian Air Force on 16 June 1943 west of Haifa. Twenty-seven men died, there were twenty-one survivors.

Wolfpacks

U-97 took part in two wolfpacks, namely.

• West (8 – 27 May 1941)
• Goeben (20 – 29 September 1941)