Convoy System: Definition, WW1 & WW2

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  • 0:44 World War I
  • 1:44 How Convoy's Worked
  • 3:08 Competing Views
  • 3:33 World War II
  • 4:00 U.S. and Britain Agreement
  • 4:35 Lesson Summary
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Lesson Transcript
Instructor: Matthew Hill
This lesson explores the history of convoy systems, how the development of submarine fleets drove convoy systems to adapt, and how the convoy system changed and evolved during the war years.

Background to Naval Convoys

The convoy system, a group of ships sailing together for protection, was designed to help protect cargo in passenger ships during the First and Second World War. The system was created out of desperation. The modern convoy system is most associated with the First World War, but it has a much longer pedigree in history. During the colonization period of the Spanish Empire in Latin America, for instance, Spain employed convoys to protect its treasure ships against marauding pirates who targeted isolated ships. Traveling in groups provided protection to ward off isolated attacks.

World War I

In the First World War, the development of the submarine ushered in a new era of naval warfare. Previously, the enemy employed surface ships to attack, but now they came from below the ocean surface. To make matters worse, the German submarines traveled in 'wolf packs', or clusters of submarines, to improve their odds of sinking enemy ships. The sinking of the RMS Lusitania in May 1915 was an especially memorable incident. This change in offensive tactics called for new defensive measures. In many ways the response was one characterized by trial and error.

The convoy system was introduced by the British in 1917 and largely centered on the English Channel. However, when the U.S. entered the war in April of 1917, ships started traveling from one end of the Atlantic to the other in the deeper open ocean.

How Convoys Worked

The general idea behind a convoy was to provide escorts for ships hauling passengers or cargo. Before the convoy system was in place, the British navy suffered massive losses at the hands of German U-boats. New technologies soon emerged along with the convoy system to meet this challenge. For example, depth charges were designed to explode underwater to destroy submarines. Also, they began to record underwater sounds to indicate the presence of submarines.

Convoys moved at different speeds. Faster convoys primarily hauled troops and were made up of large ocean liners. These convoys were more nimble and quick, and often contained a dozen ships moving in unison. Slower convoys hauled cargo and often comprised 40-50 ships. These moved slower and were more vulnerable to attack, but also carried fewer people. Convoys heading toward England departed from New York or Canadian ports and followed different routes to avoid being bunched together. The ships traveled in a zig zag pattern to confuse enemy ships, and once closer to ports were joined by destroyer fleets for protection.

Also, support ships often traveled up to 3,000 yards ahead of the main fleet to spot enemy ships before the fleet ran into them.

Competing Views

Despite the need for convoys, there were many arguments against it. First, many thought the use of convoy ships was too defensive when ships should be deployed as offensive weapons. Second, convoy ships were often slower than their combat counterparts, and the fleet could only move at the pace of the slowest ship. Third, there were rarely enough ships, which put constant strain on those tasked with building more ships.

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