Notes About the Convoy System
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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.
Britain
It was a rare convoy that had real warship escort. Most were tended by tawler equiped with deck guns stored since WWI and a few depth charges.
Warship Raiders
- Pocket Battleships : Deutschland, Nov'39 ; Graf Spee, -Dec'39 ; Admiral Scheer Oct'40-Feb'41
- Battleship-Cruiser combinations : Schorhorst and Gneisenau - early '41 ; Bismarck and Prinz Eugen
- E-Boats - raid coastal shipping and deposit mines.
Merchant Raiders 6 - 6" guns, torpedoes and some carried aircraft.
Submarines Germany and Japan each had coastal and long range submarines (each also developed extra large submarines for minelaying and cargo carrying).
The more numberous coast submarines created the most damage in direct attack and
positioning mines. But the long range
submarines are more interesting. The German U-boat and the Japanese I-boat could
Mines
Defenses
Escort for the first few hundrd miles of risky coastal waters where exposed to iarcraft, 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 perimiter of a convoy. Submarines typically traveled on the surface, sumerging ahead of a convoy and
attacking it as it passed. In the early days, submarines even attacked on the surface
at night passing between rows of ships where they were able to pick out the best targets.
When escorts were engaged in tracking individual submarines, the beauty of a wolf-pack,
simultaeous attack by multiple submarines 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.
US Experience
Coastal traffic -- backlite by city lights at tourist attractions such as Miami and New York, coastal ships were easy targets for loitering submarines. Watching the smoke on the horizon and touring the beaches for
washed up artifacts were added to the tourist attactions -- until the city fathers could be
convinced that war took presidence over play [I think there should have been executions.].
- Battle Cruisers
Alaska Class authorized in 1940, commissioned 1945, carried. 9- 12"/50 guhs ; weighed 27,500 tons ; was 808/ feet ; and 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 thought
was to use them as convoy escorts to defeat raids by Japanese
heavy cruisers. The Japanese never used their cruisers as convoy
raiders. The Germans had, and British battleships had to escort
convoys -- 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 mauraders of the German pocket battleship type that
could not risk injury far from home.
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Last updated: November 28, 2004
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