October 1944
| 3 | October | American forces broke through the Siegfried Line. |
| 4 | October | British troops landed near Patras (Greece). |
| 8 | October | British troops occupied Corinth. |
| 12 | October | British paratroopers landed at Athens. |
| 20 | October | American forces landed in the Philippines. |
| 23-26 | October | The Imperial Japanese Navy suffered a crippling defeat at the Battle of Leyte Gulf. |
| 28 | October | Bulgaria signed an armistice. |
Mediterranean
Submarine operations began to wind down in this theatre.
The midget submarine C.B.16 of the Italian Socialist Republic had sailed from Val di Figo (Pola) for a mission in the Adriatic. On 1 October, this boat was the object of a mutiny and taken over by the crew after they murdered their commanding officer, S.T.V. Giuseppe Tendi. Tendi was shot in the neck, and the three mutineers beached C.B.16 fifty metres south of the Senigallia breakwater, where they surrendered to British forces who took possession of the submarine. The three men were incarcerated in an Allied Prisoner of War camp in Algeria but would not face further charges when they were repatriated to Italy.
Giada (T.V. Mario Barazzuoli) arrived at Taranto from Colombo on 23 October. She resumed anti-submarine exercises there until the end of the war.
Atlantic
On 7th October, Atropo (T.V. Aredio Galzigna), escorted by the destroyer escort USS Frederick C. Davis (DE-136), sailed from Gibraltar for Bermuda, where she joined the US SubRon Seven [Submarine Squadron] for training exercises. During the passage, the Italian submarine submerged for a test dive, and the destroyer could not regain contact. A large air-sea rescue got underway until an Azores-based British aircraft located the submarine following her assigned route. Atropo reached Bermuda three days ahead of schedule. Frederick C. Davis would have the distinction of being the last warship lost to a U-boat in the European Theatre when she was torpedoed and sunk by U-546 on 24 April 1945.
Although Italian submarines were never equipped with Schnorkel during this war, Tito Speri is recorded to have been fitted up with a mock-up version while exercising with the escort carrier Bogue (CVE-9) and her escorts (Task Group 23.3) on 27 October.