German U-boats, raiding through the Indian Ocean, used Penang, Malaya for resupply and repair. RAF 159 Squadron Liberators, under the leadership of W/Cdr Jimmy Blackburn, set out to end Penang's usefulness as a submarine base with three 18-plus hour/3000 mile round-trip mining raids starting on 27-28 October 1944. That raid was a complete surprise, and mines from all 15 Liberators were dropped. The second raid a month later ran into a storm near Penang and was a major disappointment for the British, but a third in January 1945 was again successful.

The reference book "The Forgotten Air Force" by Air Commodore Henry Probert, strangely failed to mention the third mining op. Summarizing the effectiveness of the first two Penang ops, he wrote,

"…Unfortunately a second attempt, mounted on 26 November, encountered dreadful weather and only three aircraft managed to locate their laying areas. Nevertheless, the two operations had achieved the desired results. While no major shops were sunk by the mines, the Japanese lacked the means of clearing them, their use of the port was disrupted and most important of all the Germans decided to evacuate their base and withdraw to Batavia. [Footnote #23] The U-boat threat in the Indian Ocean had gone."

Footnote #23 states: Maritime War Narrative, pp 210-214

The book's helpful Bibliography gives further info. This narrative is The RAF in Maritime War, Vol VII, Part III, Indian Ocean Operations, November 1943-August 1945, AIR 41/75-78.

Fine-tuning it even further, I found that AIR 41/77 is the document that must contain pp 210-214. From TNA’s online catalog:

Reference: AIR 41/77
Description: Volume VII part III: the Indian Ocean and South-East Asia; operations, November 1943-August 1945. With plans and photographs.
Date: 1962

It hasn't been digitized, so I can't download it. I haven't ordered the document or found anyone to visit Kew (now open, but with severe restrictions) BUT...I wondered if an expert might be able to tell me when the U-boats left Penang for good.

Thanks,

Matt