Would Japan's Malaya or Philippine invasion fleet have been vulnerable if it ran into Dutch submarines?
Short answerIt was: O 16 sank three Japanese ships and damaged another before striking a mine three days later.
NotesThe answer corrects a counterfactual premise by pointing out that the encounter actually happened. O 16 attacked Japanese invasion shipping on 11 and 12 December 1941, sinking three vessels and heavily damaging another. She was then lost to a mine on 15 December. The compressed sequence shows both the damage one skilled Dutch crew could inflict and the mine danger that ended the boat's campaign after only days of war.