Realizing what had happened on 27 April, and aware that a slow west-bound convoy was imminent, Meise was re-configured; the easternmost boats (16 in all) formed the patrol line Star (Starling) to intercept it.

Fortress D found U-710 on the surface less than an hour later and sank it with depth charges as the U-boat attempted to fight back rather than submerge.

[4] Freighters Bornholm and Berkel collided on the evening of the 25th as a moderate west-northwest gale reduced convoy speed to two or three knots.

[5] The weather moderated enough for Duncan, Vidette and Loosestrife to refuel from the escort oiler British Lady on the 27th and a salvage tug from Iceland rescued Bornholm that evening.

Duncan and Tay made an unsuccessful depth charge attack after sighting a U-boat on the port bow at 1830.

Duncan dropped a pattern of ten depth charges; and, while turning for another attack, gained another radar contact.

Duncan gained a good ASDIC contact and dropped a pattern of ten depth charges over a visible wake.

At 0132 Snowflake approached a hydrophone contact, and U-532 was detected visually and on radar at a range of 1,300 yards (1.2 km).

Snowflake regained ASDIC contact at 1,400 yards (1.3 km) and dropped another pattern of ten depth charges.

A short time later Tay dropped depth charges on a good ASDIC contact astern of the convoy.

After one torpedo hit McKeesport on the starboard bow, Northern Gem detected U-258 and dropped three depth charges.

HMS Oribi was detached from SC127, and destroyers Penn, Panther, Impulsive, and Offa, of the 3rd Support Group under Capt.

At 2305 Snowflake made a radar contact at 3,300 yards (3.0 km) and dropped a single depth charge after the U-boat dived when illuminated by star shell.

The escorts dropped some random depth charges until dawn, and Admiral Dönitz cancelled the chase on the evening of 1 May.

This was group Finke (Finch) which was in place on 3 May numbering 27 boats, and tasked with intercepting westbound convoy SC128.

At 1400 on the 3rd Gretton was forced to take Duncan to St John's at economical speed (8 knots); and he arrived there with only 4 percent fuel remaining.

The 1st Support Group sailed from Newfoundland at midday with frigates Wear, Jed, Spey and sloops Pelican and Sennen to replace Oribi and Offa whose fuel state would become critical on the 5th.

The conning tower was still visible at a range of 80 yards (73 m); and a pattern of 14 depth charges dropped by eye caused damage requiring U-732 to return to base.

At 0122 Snowflake started closing a radar contact illuminated by star shells fired by Oribi; and both ships dropped depth charges.

Before U-125 was sunk, she sent a radio report about sinking a steamship sailing independently; and modern historians assume Lorient straggled from the convoy and was torpedoed by U-125.

[17] Northern Spray picked up 143 survivors from North Britain, Harbury, Harperly, and West Maximus by 0700 and was detached to take the rescued men to Newfoundland.

Sunflower gained an ASDIC contact at 1,200 yards (1.1 km) within minutes and destroyed U-638 with a pattern of ten depth charges before rescuing survivors from Dolius.

Tay rescued survivors from the three ships while Offa made depth charge attacks damaging U-266, which was sunk by aircraft on 15 May while attempting to reach base for repairs.

[21] At midday, Pink commanded by Lieutenant Atkinson[22] made a firm ASDIC contact 2,200 yards (2.0 km) ahead of her small convoy proceeding separately.

[23] As May 5 faded into darkness, Tay counted seven U-boats surfaced in the convoy's path; but ONS 5 was entering the fog formed where the warm Gulf Stream meets the cold Labrador Current off the Grand Banks of Newfoundland.

While pursuing an ASDIC contact, Snowflake detected U-125 on radar at 0354, observed heavy conning tower damage by searchlight at a range of 100 yards (91 m), and watched the crew detonate scuttling charges and abandon ship.

The escorts chose to continue protective patrolling around the convoy rather than attempting rescue of the U-boat crew assumed to have sunk the Lorient.

[28] At 0552 Pelican was leading the 1st Support Group to reinforce the convoy escort when it detected a radar contact at 5,300 yards (4.8 km).

Following this action, the Allies inflicted a series of defeats and heavy losses on the U-boat Arm, a period known as Black May.

The official historian, Stephen Roskill commented: "This seven day battle, fought against thirty U-boats, is marked only by latitude and longitude, and has no name by which it will be remembered; but it was, in its own way, as decisive as Quiberon Bay or the Nile.