Introduction
Convoy SC 118 was a trans‑Atlantic merchant convoy that sailed from Liverpool in the United Kingdom on 1 October 1943 and reached New York City on 16 October 1943. It was part of the Slow Convoy (SC) series that transported goods, raw materials, and troops from North America to Britain during the Second World War. The convoy carried a mixture of freighters and tankers, and was escorted by a combination of Royal Navy destroyers, corvettes, minesweepers, and an escort aircraft carrier. During its journey, SC 118 experienced several attacks by German U‑boats of the Kriegsmarine, resulting in the loss of several merchant vessels. Despite these losses, the convoy completed its trans‑Atlantic crossing, contributing to the Allied logistics effort that sustained the war effort on the Western Front and in the Mediterranean.
Background
The convoy system was instituted by the Allies in 1939 to protect merchant shipping from German naval and aerial attacks. Convoys were grouped according to speed and route, with the Slow Convoys (designated by the letters "SC") consisting of merchant ships that could maintain an average speed of about 8 knots. The SC series were organized by the British Admiralty and the American Office of Naval Intelligence, operating mainly from the east coast of Britain to North America. Convoy SC 118 was the 118th convoy in this series, following SC 117 and preceding SC 119. By late 1943, the U‑boat threat had diminished somewhat due to improved Allied anti‑submarine tactics, but the threat remained significant, particularly in the North Atlantic where German submarines were concentrated.
During the early stages of the war, U‑boat wolfpacks were highly effective at disrupting Allied shipping lanes. By 1943, however, the Allies had developed a range of counter‑measures, including the use of escort carriers, radar, sonar (ASDIC), depth charges, and improved convoy routing. The introduction of long‑range patrol aircraft from bases in the North Atlantic and the implementation of convoy escort groups with better coordination had begun to reduce the success rate of U‑boat attacks. Nevertheless, the North Atlantic remained a contested area, and convoys such as SC 118 were still at risk of being attacked by submarines, especially as German U‑boat numbers had been replenished with newer Type IX and Type XXI models capable of longer-range operations.
Convoy Composition
Merchant Fleet
The merchant fleet of SC 118 comprised 29 ships, including freighters, tankers, and cargo vessels. These ships carried a variety of goods essential for the war effort, such as raw materials, machinery, and food supplies. The majority of the ships were American and British, reflecting the trans‑Atlantic cooperation between the United States and the United Kingdom. Some of the vessels were operated by the British Ministry of War Transport, while others were privately owned or operated by the United States Maritime Commission. The convoy also carried a small number of military transport ships that were used to move troops and equipment across the Atlantic. Each ship was assigned a specific position within the convoy formation based on its speed and size.
Escort Forces
SC 118 was protected by a combination of naval escort vessels and an escort aircraft carrier. The escort group was led by the escort carrier HMS Biter (C63), a converted merchant aircraft carrier that operated a complement of 20 Fairey Swordfish torpedo bombers and 6 Grumman Avengers. The escort carriers provided air cover for the convoy, allowing continuous aircraft patrols over the convoy's approach and rear sectors. The escort group also included a force of destroyers, corvettes, and minesweepers, such as the destroyer HMS Bluebell (R56), the corvette HMS Wildrose (K19), and the minesweeper HMS Albatross (M.3). These escort vessels were responsible for anti‑submarine warfare (ASW) duties, using sonar and depth charges to detect and engage enemy submarines. The escort group also provided gunfire support and served as a deterrent against surface raiders.
Route and Schedule
Convoy SC 118 departed from Liverpool on 1 October 1943, with a scheduled arrival in New York City on 15 October. The convoy sailed southwest through the Irish Sea, then turned south to cross the North Atlantic, following a zigzag course to avoid U‑boat detection. The convoy passed near the Azores and the Cape Verde Islands before entering the Caribbean Sea. The final leg of the journey involved crossing the Caribbean and navigating the narrow waters around the Bahamas before heading into the Atlantic to arrive at New York. The convoy's overall transit time was approximately 16 days, a typical duration for a slow convoy traveling at 8 knots across the North Atlantic.
Operational History
Early Phase
In the first five days of the voyage, SC 118 sailed relatively unchallenged, maintaining a steady speed and a tight formation. The escort carrier's aircraft conducted daily patrols over the convoy's front and rear sectors, scanning for surfaced submarines and potential air threats. The escort vessels performed regular sonar sweeps, and any detected contacts were followed up with depth charge attacks. During this period, the convoy also benefited from intelligence reports indicating the absence of U‑boat activity in the expected wolfpack deployment area, allowing the escort forces to maintain a more relaxed posture.
Encounter with U‑boat Group
On 8 October, SC 118 encountered a group of German U‑boats operating in the western North Atlantic. German intelligence had directed the U‑boats to patrol the area, anticipating an incoming convoy. The first contact occurred approximately 150 miles west of the Azores. German submarine U-606 detected the convoy and closed to attack range. A surface attack was planned, but the convoy's escort carriers conducted a surprise dive, dropping depth charges that forced U-606 to submerge and retreat. Despite this, the German group continued to shadow the convoy, maintaining radio silence to avoid detection by Allied signals intelligence.
Major Engagements
On 10 October, a coordinated attack by U-606, U-631, and U-652 targeted the convoy's rear. U-606 launched a spread of torpedoes, one of which struck the freighter SS William L. MacDonald, causing a catastrophic explosion. The ship sank within minutes, taking with it the lives of 25 crew members. The escort forces responded immediately, with HMS Bluebell conducting a depth charge barrage that forced the attacking submarines to submerge deeper and break contact. During the same engagement, U-652 fired a second torpedo that missed its target, and U-631 was detected by radar and forced to surface, where it was engaged by the escort carrier's Swordfish aircraft, forcing it to dive and retreat.
In the following day, the convoy was attacked again by U-631, this time successfully striking the tanker SS Empire Harvester. The torpedo hit the forward cargo hold, causing a massive explosion that resulted in the rapid sinking of the vessel. The loss of the tanker was a significant blow, as it was carrying a cargo of aviation fuel essential for Allied operations in the Mediterranean. Escort forces, led by HMS Wildrose, conducted an intensive depth charge attack that drove U-631 away. The convoy continued its course, maintaining tight formation despite the ongoing threat.
Defensive Actions
The escort forces employed a range of anti‑submarine tactics to counter the U‑boat threat. Depth charge patterns were adjusted to cover a wider area, increasing the likelihood of damaging or destroying submerged submarines. The escort carrier's aircraft conducted both search and attack missions, using radar and visual detection to locate surfaced U‑boats. When a submarine was spotted, aircraft would deliver torpedoes or bombs, forcing the submarine to dive. Additionally, the escort vessels maintained a continuous sonar sweep, and any detected contact was quickly marked and tracked. The convoy's zigzagging course and reduced speed also made it more difficult for submarines to calculate a proper firing solution.
Losses and Outcomes
Merchant Vessel Losses
SC 118 suffered the loss of three merchant vessels during its trans‑Atlantic journey:
- SS William L. MacDonald – a 10,000‑ton freighter that was torpedoed by U-606 on 10 October. The ship sank rapidly, resulting in the loss of 25 crew members.
- SS Empire Harvester – a 7,500‑ton tanker carrying aviation fuel, torpedoed by U-631 on 11 October. The tanker sank with a loss of 14 crew members.
- SS H. P. McCormick – a 5,200‑ton freighter struck by a second torpedo from U-606 on 12 October. The ship was damaged but managed to reach port with the loss of 3 crew members.
In total, 42 merchant crew members were lost during the convoy's voyage.
Escort Losses
Although the escort forces were effective in protecting the convoy, they suffered minor losses during the engagement. HMS Wildrose sustained minor damage from depth charge explosions caused by U-631's evasive maneuvers. No crew were lost, and the ship continued to escort the convoy until it reached New York.
Submarine Losses
German U‑boats suffered significant losses during the convoy's journey. U-606, which had engaged SC 118 on 10 October, was detected and sunk by escort aircraft from HMS Biter on 12 October. The crew of U-606 was rescued by the escort destroyer HMS Bluebell and taken as prisoners of war. U-631, which had torpedoed the SS Empire Harvester, was also sunk by escort aircraft on 13 October after a prolonged engagement. The final U‑boat involved, U-652, was damaged by depth charges and forced to retreat. No German survivors were recovered from U-652.
Aftermath and Impact
Strategic Significance
The loss of three merchant vessels in SC 118 represented a moderate but tangible loss of material and human resources for the Allies. The convoy's successful completion of its trans‑Atlantic crossing ensured that essential supplies reached Britain, bolstering the war effort on the Western Front and the Mediterranean theater. The sinking of U-606 and U-631 dealt a blow to the German U‑boat fleet, reducing its operational capacity in the North Atlantic and contributing to the overall decline of the U‑boat threat during the latter half of 1943.
Strategically, SC 118's experience demonstrated the effectiveness of integrated escort protection, combining surface vessels with an escort aircraft carrier. The convoy's ability to maintain formation and repel attacks reinforced the viability of convoy tactics as the war progressed. Additionally, the loss of the SS Empire Harvester, a tanker carrying aviation fuel, highlighted the vulnerability of critical cargoes and led to increased protective measures for tankers in subsequent convoys.
Lessons Learned
Several key lessons emerged from the operational experience of SC 118:
- Integration of air and sea escorts – The presence of an escort carrier proved decisive in deterring and engaging submarines, and its aircraft could provide immediate response to surfaced threats.
- Rapid depth charge deployment – Depth charges delivered in patterns covering a wide area increased the likelihood of damaging or destroying submerged submarines, reducing the threat of successful torpedo attacks.
- Convoy zigzagging and speed regulation – Maintaining a unpredictable course and adjusting speed made it more difficult for U‑boats to calculate firing solutions.
- Intelligence coordination – Accurate intelligence regarding U‑boat positions and intentions allowed the convoy to prepare and adjust its routing to avoid known wolfpacks.
These lessons were incorporated into convoy operations throughout the rest of 1943 and into 1944, contributing to the overall decline in successful U‑boat attacks in the Atlantic.
Legacy
Convoy SC 118 is remembered as an example of both the dangers faced by merchant mariners and the effectiveness of Allied escort tactics during World War II. The convoy's experiences contributed to the development of convoy procedures and the refinement of anti‑submarine warfare techniques. Commemorative plaques in the United Kingdom and the United States honor the merchant sailors and escort crews who served on SC 118, ensuring that their sacrifice and perseverance remain part of the collective memory of the war.
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