World War I, Convoys in the Atlantic
- 1915 The British had set up a naval blockade of Germany, which began to have a telling effect: Germany was not a self-sufficient nation and was heavily dependent upon imported food, fodder, and fertilizer. Germany vowed to mount a counter-blockade, using submarines. However, the German Navy had to wrestle with a serious ethical and legal dilemma. Under international law, a warship could stop and search a merchantman; if found to be carrying contraband cargo for an enemy, a warship`s crew could capture and place a `prize crew` aboard her to sail her to an appropriate harbor. Under some circumstances, the warship could sink the merchantman, provided she had first allowed the ship`s crew to take to the lifeboats.
A submarine did not carry enough sailors to make up prize crews, so the only option was to sink the merchant ship. For this purpose, submarines were equipped with deck guns. However, if the submarine came to the surface to give fair warning, she herself became vulnerable to attack by ramming, concealed guns, or warships rushing to the rescue.
German policy went through several cycles. They played by the rules for a time, but in February, in retaliation for the indiscriminate damage of the blockade, Germany opted for `unrestricted submarine warfare`. The legal requirement for `fair notice` was met, at least in theory, by setting specifically designated war zones, within which all vessels were subject to attack without warning.
With only 35 active U-boats, Germany began sinking British merchant ships faster than they could be built, and the Germans got very serious about submarines. They launched several accelerated construction programs. One dubbed the UB class was for smaller, less capable boats that were nonetheless well suited to operations close to home.
- 1916 Toward the end of the year, the situation in Germany grew desperate. The typical daily food ration was "five slices of bread, half a small cutlet, half a tumbler of milk, two thimblefuls of fat, a few potatoes, and an eggcup of sugar". One German citizen later wrote, "If we were to starve like rats in a trap, then surely it was our sacred right to cut off the enemy`s supplies as well".
- 1917 In February, the German government announced total unrestricted submarine warfare. A note to the US government affirmed "England is using her naval power for a criminal attempt to force Germany into submission by starvation" and warned that Germany was now compelled to use "all the weapons which are at its disposal". The German government knew that this would most likely bring America into the war but predicted that Britain would be forced to the peace table before American forces could have much effect.
Great Britain had the world`s largest merchant fleet, almost half of the world total, but British shipbuilding capacity was only about 650,000 tons a year. By March, U-boats were sinking almost 600,000 tons a month and Great Britain was down to a six-week food supply.
The US entered the war in April.
- 1917 One time-honored method existed for protecting merchant ships from enemy attack: the convoy, dating back almost to the dawn of ocean commerce. The British Navy resisted, however. Too many ships were coming and going, 2,500 a week, and port facilities were already strained; bringing in the glut of a convoy would create chaos. The convoy would also become a huge target for U-boats. Convoying might be all right for military auxiliaries such as troopships, but merchant crews did not have the skills necessary to keep in convoy formation, and many did not speak English. Most merchant ships were fast enough to outrun a U-boat anyway. Perhaps most significant, warships would likely be out looking for the enemy, not herding a bunch of merchantmen. The Navy was trained for offense, not defense, the argument went, to be aggressive, not passive.
The counterarguments: Most of the traffic consisted of small coasters and ferries; only about 140 trans-ocean ships were arriving each week, spread across a number of ports. A U-boat could only make one attack before the escorts would force it to break off and hide; the larger the convoy, the more ships would be home free. Also, a merchantman might outrun one U-boat right into the arms of another. Crews could be trained. The goal was to curtail sinking, not make naval officers feel good.
By late spring, the situation was grave enough that Navy officials finally agreed to a convoy trial. They never looked back. Of 83,959 ships in convoys from then to the end of the war, U-boats only sank 257. During the same period, U-boats sank 2,616 independent sailers. A convoy`s main benefit: It forced the U-boats to attack submerged, which meant they already had to be in attack position if a convoy happened to sail past.
Convoys with air patrol were the safest of all, because the submariners knew that if they carried out an attack, the aircraft could determine their approximate.
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