Bercuson David Jay - Deadly seas: the duel between the St. Croix and the U305 in the Battle of the Atlantic

At mid-afternoon on 15 September 1943, HMCS St Croix, a destroyer built in the United States during the First World War, steams out of Plymouth as part of Escort Group ( EG) 9. The Senior Officer of the Escort is aboard HMS Itchen, a Royal Navy frigate specifically built to hunt U-boats.

It is a beautiful sunny day but, after leaving the calm waters of the harbour, the escort vessels begin to rise and fall on a heavy swell. The wind picks up. The men aboard the St Croix wonder where they are going. Some say the Mediterranean, others the Bay of Biscay. No one but her Captain, Lieutenant-Commander Andrew Hedley Dobson, Royal Canadian Naval Reserve, really knows. After passing Lands End, the group shapes course for the Western Approaches. Dobson tells his officers that EG9 is due to rendezvous with inbound convoy HX256 some 500 miles west of Ireland.

At dawn on the 17th, EG9 sights HX256 . St Croix and the other escorts sweep the flanks of the convoy, making sure that all is right aboard the plodding merchantmen. She then assumes her assigned place in the escort screen. Just before midnight, new orders flash to EG9 from the Commander-in-Chief Western Approaches: If HX256 is not threatened, leave at dawn on 19 September and proceed to support westbound convoy ONS18. Signals intelligence strongly indicates there is a large group of u-boats in its path.

Precisely at dawn, Itchens signal lamp blinks out a message to St Croix and the other vessels of EG 9 Execute course change on my signal. A signal flag is hauled up on her yardarm, and similar flags soon flutter on the other ships. At precisely 6:45 a.m., the flags snap down and the escorts heel over and pull away from the convoy. They head north at 12 knots, with Itchen in the lead. At 3:50 p.m. the Admiralty informs Itchen that EG9 is being tracked by the Germans and suggests that she and her consorts approach the convoy by an evasive route.

EG9 changes course and steams ahead into nightfall. Aboard St Croix, Dobson warns his officers that something big is up, but he decides not to call the ship to action stations. He knows there will be many long hours at full alert in the coming hours of darkness, and he does not want to disturb the ships routine until he absolutely has to. But he doubles the watch, tells anti-submarine officer Lieutenant John F. Gallagher to pay close attention to the asdic, and checks that the radar set is working properly. What Dobson does not know is that the Admiralty has ordered ONS18 to rendezvous with ON202, a somewhat faster convoy steaming westward on a parallel course some miles to the north. This order is issued as evidence mounts of a major submarine attack against one or both of the convoys.

Soon St Croix spots convoy ONS18 and takes up a position on its outer screen. At 9:45 a.m. five very long-range B -24 Liberators of the Royal Air Force 120 Squadron from Iceland fly over. Aircraft X120 makes the first positive spotting of a grey wolf 15 miles north of ON202. From noon until nightfall of the 20th, the two convoys try to join together. It is a slow and difficult process when it is done this way, at sea and en route, and has its share of confusion and chaos. But it is done, and the combined convoy ONS 18/ ON202 is made up of eighty-eight merchant vessels guarded by seventeen escorts. It is among the largest convoys of the war.

Four days earlier, at midnight on 1516 September 1943, Grand Admiral Karl Dnitz, Commander-in-Chief of the German navy, the Kriegsmarine, had ordered the formation of Group Leuthen, a concentration of twenty u-boats, against what he suspected was a westbound convoy. All the submarines in this wolfpack are equipped with the new acoustic Zaunknig (wren) torpedo. In the middle of the line is U305, commanded by Lieutenant Rudolf Bahr. Shortly before midnight on 1920 September, one of the submarines sights convoy ONS18. The Great Lion, as Dnitz is idolized throughout the u-boat service, knows that the moment has arrived. To Leuthen, he radioes, At em!

Bahrs U305 is on the surface at 12:48 a.m. when a lookout spots an aircraft with Leigh Lights approaching fast. Two minutes later, the boat next to him, U270, spies several dark shadows to the north. It is a second convoy! Just before 3 a.m., U270 draws first blood: its wren torpedo blows off the stern of the Royal Navy frigate HMS Lagan at a range of 1.8 miles. It is a triumphant inauguration for Dnitzs new destroyer cracker, which the Allies quickly dub the gnat.

Dnitz now orders all Leuthen boats to concentrate against ON202. At 4 p.m. on 20 September about six submarines charge the enemy cavalry style, flak firing furiously, in an attempt to break through both air cover and escort screen to get inside ON202. Forty ships in ten serried columns: a target-rich environment! Dnitz urges the U-boats on: Remain surfaced and proceed to convoy at full speed.

Bahr is frustrated. The battle is raging all around him, but U305 just cant get a fix on any hostile target. He searches the vast expanses of the ocean for ON202. At 5:20 p.m. one of U305s lookouts spots an aircraft approaching. There are no German Luftwaffe planes way out here, so the alarm is called: Captain to the bridge! Aircraft approaching. West by northwest at 12,000 metres.

Bahr springs into action: Emergency! Dive! Dive! Chief, level off at 100 metres!

U305 plunges beneath the surface. The bastard hasnt seen me, Bahr gloats, as no bombs crash around his boat. At 5:45 p.m. he resurfaces and rushes to the bridge. He later records: Freighter at 2500 metres. I approach. Soon discover a destroyer screening the freighter. Bahr dogs the smoke clouds on the horizon, hoping to get a good shot in later under cover of darkness.