Convoy ONS 5

ONS 5 was the 5th of the numbered ON/ONS convoys of Slow trade convoys Outbound from the British Isles to North America. The North Atlantic battle around it in May 1943 is regarded as the turning point of the Battle of the Atlantic in World War II. The battle ebbed and flowed over a week and involved more than 50 Allied ships and their escorts, against more than 30 U-boats. It saw severe losses on both sides and was almost the last Allied convoy to do so. Losses inflicted on the U-boats became a besetting feature of the campaign. It is seen as the point when the tactical and strategic advantage passed to the Allies, ushering in the period known to the Kriegsmarine as Black May.