Notes About the Convoy System

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Draft 2

The British convoy system was set up in WWI and reactivated for coastal shipping with the first month of the war in Europe. The principle of the convoy was to concentrate shipping where it could be protected by all available armed escorts. Convoys did protect ships, but at a cost of almost 30% of tonnage carried while ships waited for convoys to gather. Dangers to convoys were many: warship raiders, merchant raiders, air craft and submarines. It was a rare convoy that had real warship escort. Most were tended by trawlers equipped with deck guns stored since WWI and a few depth charges.
Warship Raiders .
• Battleships, Battle Cruisers, and Pocket Battleships made raids on British Convoys. : Deutschland (Lutzow) - Oct-Nov'39 ; Graf Spee - Oct--Dec'39 ; Admiral Scheer, - Oct'40-Feb'41 ; Admiral Hipper - Dec'40, Feb'41, Dec'42 ; Schorhorst and Gneisenau - Dec'39, June'40, Nov'40, Jan '41 ; Bismarck and Prinz Eugen - May'41 ; Tirpitz - Mar'42.
• E-Boats - raid coastal shipping and deposite mines.

Merchant Raiders .Typically well built refrigerator ships with six 6" guns, torpedoes, and spotting aircraft. Attacked merchant ships sailing alone to add to the reason for convoys. Germany sent out 12 merchant cruisers to every ocean with much success. Japan prepared 14 commercial raiders with little success..
Submarines . Germany and Japan each had coastal and long range submarines (each also developed extra large submarines for minelaying and cargo carrying). The more numerous coast submarines created the most damage in direct attack and positioning mines. But the long range submarines are more interesting. The German U-boats was smaller that the U.S. submarine ; U-boats were designed to blockade England and the Baltic. The could reach U.S. waters by refueling from mother ships. The Japanese I-boats were larger than U.S. subs intended to travel the vast Pacific. They were poorly operated compared to the Germans or by the Americans in the later war years.
Mines . MInes needed only to be observed to close a port and to force travel away from potential mine fields, thus increasing the area to be defended against. Mies were lain by ships, aircraft and submarines. Several U.S. East Coast ports were closed to mines in 1942.

Defenses

Escort was provided for the first few hundred miles of risky coastal waters where exposed to aircraft, coast submarine, and E-boats, then the escorts had to turn back to accompany the next convoy. Some protection could be provided by aircraft for another hundred miles and then the convoy was on its own for over half of its journey and exposed to long-range submarine attack.
Asdic/Sonar could cover the mile in front of an escort -- of the 50-75 mile perimeter of a typical convoy. Submarines typically traveled on the surface, submerging ahead of a convoy and attacking it as it passed. In the early days, German submarines even attacked on the surface at night passing between rows of ships where they were able to pick out the best targets. While escorts were engaged in tracking individual submarines,the beauty of a wolf-pack unfolded with, simultaneous attack by multiple submarines that could overwhelm the defenses and torpedo many ships. Often the convoy was told to scatter, so that the distance between targets would slow down the German attacks.

U.S .Experience

Coastal traffic -- backlit by city lights at tourist attractions such as Miami, Charleston, and New York, coastal ships were easy targets for loitering submarines. Watching the smoke of burning ships on the horizon and touring the beaches for washed up artifacts were added to the tourist attractions -- until the city fathers and businessmen could be convinced that war took precedence over play and profit. I[ think there should have been executions.]. Merchant ships did not like waiting for a convoy to formed, those that aragantly when ahead independently were easy targets..
• Battle Cruisers Alaska Class authorized in 1940, commissioned 1945, carried nine 12"/50 guns ; weighed 27,500 tons ; was 808 feet ; with speed of 33 knots.
  The battle cruisers, Alaska, (CB-1) and Guam ,(CB-2), were intended to be "cruiser killers" to outgun the Japanese 8" cruiser with a larger ship, yet was still be smaller, faster and cheaper than a full sized battleship. The thinking was to use them as convoy escorts to defeat expected raids by Japanese heavy cruisers. The Japanese never used their cruisers as convoy raiders. The Germans had, and British battleships had to escort high value convoys . Those used were old battleships too slow for fleet duty, but with the weight of shell to keep raiders away from merchant ships.
      The battle cruiser as a class had not fared well in WWI where, on the battle line, they were shown to be more vulnerable to damage than a battleship and without sufficient weight of broadside to sink enemy battleships. As an extra-heavy cruiser, they have been fast enough to chase down and to outgun other cruisers and to chase off marauders of the German pocket battleship type that could not risk injury far from home.
  

  Atlantic Convoy Designations

  Designation	Description			Usual Route
  	Number of 
  	Convoys
  
  East Bound
  SC	177  	Slow convoy (less than 8 Kn)	Halifax to UK
  HX	377 	Fast convoy (9-13 Kn)		Halifax to Liverpool
  CU	 74	Very Fast convoy (14Kn) 	CN/NY to UK	Originally Curacao tankers under USN protection
  
  O= outbound from UK
  OA	226	Southern UK to Canada
  OB	346	Liverpool to  N or S America
  OG	117	UK by way of Gibraltar
  ON 	307	UK to North America (Halifax)
  OS	185	UK to South Atlantic (Freetown)  see KMS
  
  HA	157	Halifax to Aruba (Caribbean)
  HG	117	High speed Gibraltar to UK 
  HK	183	High speed Galveston to Key West
  
  SL 	275	Slow convoy South Atlantic (Freetown) to UK
  HG	117	High speed by way of Gibraltar
  MKS 	162	Med thru Gibraltar to UK  (Operation Torch) Slow
  MKF	57	Med to UK Fast
  KMS	169	UK to Med Slow
  KMF	55	UK to Med Fast
  
  PQ	41	Iceland to Archangel,USSR ;  later JW series
  QP	39	From Russia ;  became RA series
  South Atlantic and Mediterranean convoys would often join or separate at Gibraltar.
  
  NK	164	New York to Key West
  NG 	207	New York to Guantanamo (Cuba)
  GK	163	Guantanamo to Key West
  GN	207	Guantanamo to New York
  GZ	139	Guantanamo to Panama Canal
  ZG	141	Panama Canal to Guantanamo
  

  UK. The year ends with USN actually convoying British troops on American ships escorted by battleships and aircraft carrier..
  
  Notes:
  There were also regional convoys with their own convoy series. Series were not consistent.
  W as first letter indicated troop convoy.
  A good reference: The Website for Merchant Ships during WW2
  One can easily see why so many escort ships were required.
  
  There was never any question which side the US was on in the European conflict that began Sept 1, 1939 with the invasion of Poland. From the onset USN ships reported all Axis ships observed. These were broadcast in the clear so that British cruisers could come capture the German passenger liners and merchantmen from the Caribbean trying to return to home port. U.S. destroyers operated on relays to report current locations and would stand by to take off passengers and crew as the Germans would scuttle their ships off the U.S. coast rather than be taken as prize of war. On Sept 3, USN organized a Neutrality Patrol to 300 miles from U.S. shores Forty reserved destroyer were recommission for scouting duty. On Sept 13 the first Neutrality Patrol set sail -- the effect was to relieve the Royal Navy from duty in American waters.
      The U.S. involvement gradually escalated in 1940 as German conquered France and the Low Countries. 35 more reserve destroyers were recommissioned. FDR promised all aid short of war. Authorization to build a two-ocean navy. German armed raider traveled to the Pacific thru Arctic waters lead by Soviet ice breaker. U.S. gives 50 restored destroyers to Britain in exchange for bases from which to patrol the Atlantic and Caribbean.
      By 1941 U-boats sink ships faster than they can be replaced. Six merchant raiders were still at sea plus battleship raiders. USN organizes support force to MOMP, Mid Ocean Meeting Point. Quarter of Pacific Fleet ordered to Atlantic on patrol expanded to 3/4 of that ocean. When Bismarck penetrates into western Atlantic FDR orders battleships to Iceland and to shoot-on-sight any Axis ships. Combat with USN destroyers vs. U-boats; destroyer sunk. Begin transfer of escort carriers to

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  Drafted Nov 28, 2004 Last updated: November 1, 2015, add convoy designations.
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