Convoy ONS 5 facts for kids

Quick facts for kids Convoy ONS 5
Part of World War II
Date 29 April-6 May 1943 Location North Atlantic Result British Victory
Belligerents
Germany	United Kingdom  Canada
Commanders and leaders
Admiral Karl Dönitz	Convoy Comm: JK Brook RNR Escort B7: Cdr Peter Gretton
Strength
Star 16 U-Boats Finke 27 U-boats	42 ships 7 escorts
Casualties and losses
7 U-boats sunk 7 U-boats damaged	13 ships sunk (63,000 gross register tons (GRT))

ONS 5 was a slow-moving group of supply ships, called a convoy, that sailed from the British Isles to North America during World War II. This particular convoy, ONS 5, faced a huge battle in the North Atlantic in May 1943. This fight is seen as a major turning point in the Battle of the Atlantic.

The battle lasted for about a week. More than 50 Allied ships and their escorts, along with over 30 German U-boats (submarines), were involved. Both sides suffered heavy losses. However, after this battle, Allied convoys rarely faced such big losses again. Instead, the German U-boats started taking more damage. This battle marked when the Allies gained the upper hand. It led to a period the German navy called Black May, because they lost so many submarines.

How the Battle Started

ONS 5 was a convoy of 43 ships. They were traveling from Liverpool in the UK to Halifax in Canada. These ships were either empty or carrying goods for trade. The convoy left Liverpool on April 21, 1943. It would arrive in Halifax three weeks later, on May 12.

The convoy was led by JK Brook RNR, who was the Convoy Commodore. He sailed on a Norwegian ship called Rena. The convoy was protected by seven warships from Escort Group B7. This group was led by Captain Peter Gretton on the destroyer Duncan. Other ships in the group included the destroyer Vidette, the frigate Tay, and the corvettes Sunflower, Snowflake, Loosestrife, and Pink. Two rescue trawlers, Northern Gem and Northern Spray, also joined them. A fleet oiler, British Lady, was there to refuel the warships at sea. More escort ships joined as the battle went on.

At this time, many Allied convoys were at sea. The Germans had 58 U-boats waiting in three patrol lines. One group, called Star, had 16 U-boats. On April 28, 1943, U-650 spotted ONS 5. The Star group quickly gathered to attack the convoy.

Ships in the Fight

ONS 5 had 42 merchant ships and 16 escort warships. Not all of them were present for the entire battle. In the end, 13 merchant ships were lost during the seven-day fight.

The German U-boat groups, Star and Finke, had 43 U-boats in total. Again, not all of them were in contact throughout the battle. Six of these U-boats were sunk by the Allies.

The Battle Unfolds

The merchant ships left Liverpool on April 21, 1943. Escort Group B7 met them on April 22. The convoy formed up in strong winds and rough seas. On April 23, the weather got even worse. It became very hard for the ships to stay in their positions.

First Attacks

On April 24, a Flying Fortress aircraft from the RAF spotted a diving U-boat. It dropped depth charges. Less than an hour later, another Fortress found U-710 on the surface. The U-boat tried to fight back but was sunk by depth charges. U-710 was very close to the convoy, but probably didn't know it.

Rough Seas and New Codes

On April 25, two freighters, Bornholm and Berkel, crashed into each other in a gale. Bornholm started taking on water and left the convoy. The weather was so bad that the convoy could only move very slowly. On April 26, German U-boats changed their secret code for messages. Allied intelligence could not read these messages until May 5. This made it harder for the Allies to know what the U-boats were planning.

Intense Fighting (April 28–29)

On April 28, ONS 5 entered the area where the Star U-boat group was waiting. U-650 spotted the convoy. Even though aircraft forced it to dive several times, U-650 kept track of the convoy. By nightfall, other U-boats joined U-650. Commander Gretton knew the U-boats were nearby.

As darkness fell, the U-boats attacked. The escort ships used their radar and ASDIC (sonar) to find the submarines. Sunflower and Duncan made several attacks, dropping depth charges. U-532 launched torpedoes at Snowflake, but missed. U-532, U-386, and U-528 were all damaged by these attacks. They had to return to their bases. U-528 was later sunk by an aircraft.

On April 29, U-258 torpedoed the ship McKeesport. The ship was abandoned and sunk by the escorts to prevent Germans from finding secret documents. Northern Gem rescued almost all the crew. U-258 was also damaged and had to go back to base. The British sent more destroyers to help ONS 5. The weather got much worse, turning into a full gale.

Storm and Fuel Problems (April 30 – May 3)

On April 30, ONS 5 was moving very slowly in a huge storm. Some ships were scattered far from the convoy. The escort ships worked hard to gather them back. The destroyers started running very low on fuel because of the storm. On May 3, Captain Gretton had to take his ship, Duncan, to St John's for fuel. He arrived with only 4% of his fuel left. Lieutenant-Commander RE Sherwood took command of the escort group on HMS Tay. However, the sonar on Tay stopped working right after he took command. Other destroyers also had to leave for refueling.

The Fog of War (May 4–5)

By May 4, the weather improved a bit. ONS 5 was now moving faster, but it was down to 30 ships and 7 escorts. The other ships were sailing on their own. A new group of U-boats, called Finke, was formed to attack another convoy. But U-628 from this group spotted ONS 5. Two U-boats were attacked by Canadian aircraft. One, U-209, was damaged and later sank.

On May 4, Vidette found U-514 on radar and damaged it with depth charges. U-514 was out of the battle. U-707 torpedoed the ship North Britain. Vidette also damaged U-732, forcing it to return to base.

On May 5, the U-boats launched many torpedoes. Harbury, Harperly, and West Maximus were hit. Bristol City and Wentworth were also torpedoed. The ship Lorient went missing, likely sunk by U-125. Rescue ships picked up many survivors. Sunflower found and destroyed U-638 with depth charges. Tay rescued survivors from Dolius. Later, Selvistan, Gharinda, and Bonde were hit by torpedoes from U-266. Selvistan and Bonde sank quickly. Tay rescued survivors. Offa damaged U-266, which was later sunk by aircraft.

The Turning Point (Night of May 5–6)

As May 5 turned into May 6, ONS 5 entered a thick fog. This fog formed where warm and cold ocean currents met. Visibility dropped to almost nothing. But the British ships had special radar that could see through the fog, while the U-boats could not. This gave the Allies a huge advantage.

Many U-boats were lost during this foggy night.

• Vidette attacked and likely destroyed U-531.
• Loosestrife attacked and probably destroyed U-192.
• Oribi crashed into U-125. Snowflake later found the damaged U-125 and saw its crew abandoning ship. The escorts focused on protecting the convoy, not rescuing the U-boat crew.
• Vidette attacked and likely destroyed U-630.
• Sunflower rammed U-533, damaging it. Both ships were able to repair and stay at sea.
• Pelican attacked and likely destroyed U-438.

The German U-boat group Finke was losing too many submarines. Realizing his mistake, Admiral Dönitz called off the attack on May 6. He ordered the Finke group to retreat.

What Happened Next

Over a week, ONS 5 had been attacked by more than 40 U-boats. The Allies lost 13 ships, but the escorts managed to sink 6 U-boats and seriously damage 7 others.

This battle showed that the convoy escorts had become very good at protecting their ships. They had better weapons and more experience. From now on, they could not only defend convoys but also cause big losses to the attacking U-boats.

ONS 5 was a major turning point in the Battle of the Atlantic. After this, the Allies kept winning against the U-boats. This period is known as Black May because of the huge losses the U-boat fleet suffered. Eventually, Admiral Dönitz had to pull his forces out of the North Atlantic.

The official historian, Stephen Roskill, said that this seven-day battle, fought against 30 U-boats, was as important as famous naval battles like Quiberon Bay or the Nile.

Ships Lost

Allied ships lost

Date	Name	Nationality	Casualties	Tonnage	Sunk by
29 April 1943	McKeesport	United States	1	6,198	U-258
4 May 1943	Lorient	United Kingdom	46	4,737	U-125
4 May 1943	North Britain	United Kingdom	29+	4,635	U-707
5 May 1943	Harbury	United Kingdom	7	5,081	U-628
5 May 1943	West Maximus	United States	5	5,561	U-264
5 May 1943	Harperley	United Kingdom	11	4,586	U-264
5 May 1943	Bristol City	United Kingdom	15	2,864	U-358
5 May 1943	Wentworth	United Kingdom	5	5,212	U-358
5 May 1943	Dolius	United Kingdom	4	5,507	U-638
5 May 1943	West Makadet	United States	0	5,565	U-584
5 May 1943	Selvistan	United Kingdom	6	5,136	U-266
5 May 1943	Gharinda	United Kingdom	0	5,306	U-266
5 May 1943	Bonde	Norway	5	1,570	U-266

U-boats lost

See also

• Convoy Battles of World War II