Convoys ONS 18/ON 202

ONS 18 and ON 202 were North Atlantic convoys of the ONS/ON series which ran during the battle of the Atlantic in World War II. They were the subject of a major U-boat attack in September 1943, the first battle in the Kriegsmarine's autumn offensive, following the withdrawal from the North Atlantic route after Black May.

Background

Following the defeats of May 1943, and the devastating losses incurred by the U-boat Arm (U-Bootwaffe, or UBW) Admiral Dönitz had withdrawn from attacks on the North Atlantic route while awaiting tactical and technical improvements. Chief among these was the T-5 acoustic torpedo, with which (it was planned) the convoy escorts could be attacked and eliminated, leaving the merchant ships defenceless. By September 1943 these were ready, and U-boat Control (Befehlshaber der Unterseeboote, BdU) dispatched

a patrol group of 21 boats, code-named Leuthen, to renew the attack on the North Atlantic route.

Ships involved

In September 1943 BdU had established the patrol line Leuthen of 21 U-boats south of Greenland; these were to intercept west-bound convoys as they were about to enter the Greenland Air Gap, where Allied aircraft were reckoned to be unable to operate due to the extreme range. Leuthen was to harry any convoy it encountered while crossing the gap, before breaking off to repeat the onslaught with the east-bound convoys.

On 12 September 1943 convoy ONS 18 left Liverpool bound for Halifax.

Composed of 27 ships it was protected by B-3 Escort Group, comprising 2 destroyers, Escapade and Keppel, the frigate Towy ( Cdr MB Evans RN, the Senior Officer:Escort), and 5 corvettes; Narcissus, Orchis, Roselys, Lobelia and Renoncule.

ONS 18 was also accompanied by the MAC carrier Empire MacAlpine.

When Western Approaches Command became aware of Leuthen, it was decided to reinforce ONS 18; the following convoy, ON 202 was ordered to close up, and a support group, SG 9, sent to join.