'Oder' (ii) was a U-boat wolfpack operation in the Atlantic against the HX.238 convoy (17/19 May 1943).
The wolfpack comprised U-221, U-228, U-336, U-558, U-603, U-642, U-666 and U-752, and neither lost any of its own number nor sank any ship.
On 17/18 May the B-Dienst signals intercept and decryption service was able to establish the nature of the evasive movements being undertaken by the HX.238 and SC.130 convoys, and as a result the 'Donau' and 'Nahe' wolfpacks were ordered to move farther to the south as a new patrol line whose length was increased southward by the addition of the newly established 'Oder' (ii) wolfpack. However, the HX.238 convoy of 45 ships supported by the Canadian Escort Group C3 (destroyers Skeena and British Burnham, and corvettes Bittersweet, Eyebright, La Malbaie and Pictou) and, within the convoy, the escort carrier Fencer on transfer to the UK, passed by the patrol line without being located.
The following SC.130 convoy of 38 ships supported by Commander P. W. Gretton’s British Escort Group B7 (destroyers Duncan and Vidette, frigate Tay, and corvettes Loosestrife, Pink, Snowflake, Sunflower and, until 19 May, Canadian Kitchener) was sighted and reported during the night of 18/19 May by U-304, which was able to bring up U-645 and U-952. The Germans lost contact with the convoy in the morning as the result of the latter’s sharp change of course, however.
Air escort, provided by Consolidated Liberator long-range patrol bombers of the RAF’s No. 120 Squadron, then frustrated the U-boats' efforts to regain contact: a Liberator attacked but failed to damage U-731, which was nonetheless just one of the six boats compelled to dive. One of these, U-952, was depth-charged and badly damaged by Tay.
Oberleutnant Wilhelm-Heinrich Graf von Pückler und Limburg’s U-381 was lost at this time to unknown causes.
While preparing for a submerged attack, U-636 was detected by Snowflake and attacked with the help of Duncan as the ships covered the area several times with depth charges, but was not damaged. Two other boats escaped Pink and Sunflower on the surface. At about 12.00 the British 1st Support Group (frigates Wear, Jed and Spey, and sloop Sennen) came up from astern on the convoy and spotted two U-boats. One of them, Kapitänleutnant Odo Loewe’s U-954, fired torpedoes as it dived but was sunk by the 'Hedgehog' anti-submarine bombs of Sennen and Jed. Duncan prevented an attack by U-707, which was damaged. A Liberator of No. 120 Squadron, in co-operation with Vidette, forced six boats to dive, and another two Liberator aircraft of No. 120 Squadron compelled four and two U-boats to dive, and bombed three of these six boats.
Before dusk, Jed and Spey drove off the last contact-keeper: only U-92 was in a position to attack, and missed. During the morning the Germans broke off the operation and a Liberator sank Kapitänleutnant Wilhelm von Mässenhausen’s U-258.
The remaining boats were then formed into the 'Mosel' wolfpack.