Yashimoto's Last Dive

The C-in-C Eastern Fleet had further reason to be perturbed by losses in the Indian Ocean. Many sinkings by the Japanese were marked by atrocities. The blood lust of their submarine commanders seems to have grown as their losses multiplied… it was commonplace for ships’ crews to be machine-gunned in boats and rafts.

War in the Southern Oceans 1939–1945

Turner, Gordon-Cumming & Betzler (Oxford University Press, 1961)