In the early weeks of World War II, the Royal Navy was engaged in efforts to patrol and secure vital maritime routes against the growing threat of German naval forces. On September 10, 1939, this effort would take a tragic turn when submarines HMS Oxley and HMS Triton were operating in the North Sea near Norway. While patrolling the area, HMS Triton mistook HMS Oxley for an enemy vessel and launched a torpedo strike.HMS Oxley, commanded by Lieutenant Commander H. C. H. Thomas, sank quickly after being struck by the torpedo. Of the 53 crew members aboard, only a few survived, further compounding the tragedy as the Royal Navy faced its first submarine loss of the war. The incident underlined the dangers of misidentification in naval warfare, particularly in the unclear environment of submarine engagements where visibility and recognition could be severely limited.The sinking of HMS Oxley was a harsh reminder of the perils associated with military operations at sea, where friendly units could inadvertently target each other, especially during the fog of war. It prompted the Royal Navy to review and improve its identification procedures and communication protocols to prevent similar occurrences in the future, highlighting a significant operational lesson learned early in the conflict.