Convoy ON 127
Convoy ON 127 was a trade convoy of merchant ships during the second World War. It was the 127th of the numbered series of ON convoys Outbound from the British Isles to North America and the only North Atlantic trade convoy of 1942 or 1943 where all U-boats deployed against the convoy launched torpedoes. The ships departed Liverpool on 4 September 1942 and were met at noon on 5 September by the Royal Canadian Navy Mid-Ocean Escort Force Group C-4 consisting of the and the with the s,,, and. St. Croixs commanding officer, acting Lieutenant Commander A. H. "Dobby" Dobson RCNR, was the senior officer of the escort group. The Canadian ships carried type 286 meter-wavelength radar but none of their sets were operational. Celandine carried Type 271 centimeter-wavelength radar. None of the ships carried HF/DF high-frequency direction finding sets.
Background
As western Atlantic coastal convoys brought an end to the second happy time, Admiral Karl Dönitz, the Befehlshaber der U-Boote or commander in chief of U-Boats, shifted focus to the mid-Atlantic to avoid aircraft patrols. Although convoy routing was less predictable in the mid-ocean, Dönitz anticipated that the increased numbers of U-boats being produced would be able to effectively search the area with the advantage of intelligence gained through B-Dienst decryption of British Naval Cypher Number 3. However, only 20 percent of the 180 trans-Atlantic convoys sailing from the end of July 1942 until the end of April 1943 lost ships to U-boat attack.Initial contact
Wolf pack Vorwarts was forming about 500 miles west of Ireland as the convoy left Liverpool.,,,,,,,,,,,, and formed a search line across the convoy's path just beyond the range of land-based aircraft. U-584 reported the convoy on 9 September, but lost contact that evening.10 September
U-96 regained contact on 10 September and torpedoed the Norwegian tanker Svene, the tanker F.J.Wolfe and the Belgian freighter Elisabeth van België in a single submerged daylight attack. Sherbrooke fell back to aid the torpedoed ships while St. Croix, Ottawa, and Celandine searched unsuccessfully for U-96. F.J.Wolfe was able to regain its station with the convoy. Ottawa continued to patrol astern of the convoy after St. Croix and Celandine resumed their normal patrol stations.A coordinated night attack on the convoy began with U-659 torpedoing the British tanker Empire Oil on the evening of 10 September. St. Croix made SONAR contact immediately prior to the attack and Celandine, Ottawa, and St. Croix searched for U-659 after the attack. St. Croix and Ottawa fell back to rescue 23 of the stricken tanker's crew of 41. U-404 torpedoed the tanker Marit II, U-608 launched torpedoes which missed the convoy, U-218 torpedoed the tanker Fjordaas, and U-92 and U-594 launched torpedoes which missed the convoy before Ottawa, St. Croix, and Celandine rejoined the convoy. Sherbrooke remained astern of the convoy aiding the ships torpedoed by U-96, and rescued all but one of the crew of the sinking Svene and Elisabeth van Belgie. The remaining escorts counter-attacked, and depth charge damage forced U-659 and U-218 to return to port. Both Marit II and Fjordaas were able to regain their stations in the convoy. Empire Oil was later sunk astern of the convoy by U-584.