Convoy ON 127

Convoy ON 127
Part of Battle of the Atlantic
HMCS Ottawa
Date 9–14 September 1942 Location North Atlantic Result German tactical victory
Belligerents
United Kingdom Canada	Germany
Commanders and leaders
RADM Sir E O Cochrane KBE LCDR A.H. "Dobby" Dobson RCNR	Admiral Karl Dönitz
Strength
35 freighters 4 destroyers 4 corvettes	13 submarines
Casualties and losses
6 freighters sunk (44,113GRT) 24 killed/drowned 1 destroyer sunk 114 killed/drowned

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 Canadian River class destroyer Ottawa and the Town class destroyer St. Croix with the Flower class corvettes Amherst, Arvida, Sherbrooke, and Celandine.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.

As western Atlantic coastal convoys brought an end to the second happy time, Admiral Karl Dönitz, the Befehlshaber der U-Boote (BdU) 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.

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