Unrestricted submarine warfare

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Unrestricted submarine warfare is a type of naval warfare in which submarines sink merchant ships without warning.

There have been three major campaigns of unrestricted submarine warfare:

The First Battle of the Atlantic during World War I (waged intermittently by Germany between 1915 and 1918). (Ostensibly the casus belli for the U.S. entry into World War I in 1917.)
The Second Battle of the Atlantic during World War II (1939–1945). (waged by Germany)
The Pacific War during World War II (1941–1945). (waged by the U.S.)

1 World War I
2 Unrestricted submarine warfare and the laws of war
3 See also
4 Footnotes

[edit] World War I

Main article: First Battle of the Atlantic

The evidence suggests that Germany had not started World War I with an appreciation of the impact on commerce and supply that submarines could have. They had less than 30 operational boats, all with small torpedo capacities. At first, merchant ships would be stopped, occupants safely evacuated and then the vessel sunk, usually by gunfire, all following Prize Rules. This had little effect and increasingly placed the German submarine—U-boat—at risk from defensive weaponry.

Germany had practical strategic problems. War-weariness affected the German home situation. The best chance of achieving an early advantageous peace with Britain was to stifle its trade and imports. Surface ships had not been effective, neither could the German Navy force the Royal Navy off the seas—the Battle of Jutland had shown this, despite an apparent German victory.

The gamble which was taken was that unrestricted submarine warfare would critically damage Britain before an incensed United States could make a practical impact. In the event, it failed.

[edit] Unrestricted submarine warfare and the laws of war

The submarine sinking of merchant ships without warning are in violation of the 1930 First London Naval Treaty, which specifies that "...except in the case of persistent refusal to stop on being duly summoned, or of active resistance to visit or search, a warship, whether surface vessel or submarine, may not sink or render incapable of navigation a merchant vessel without having first placed passengers, crew and ship's papers in a place of safety. For this purpose the ship's boats are not regarded as a place of safety...."

However, the London Rules were obsolete before they were signed (though the Kriegsmarine based its Prize Rules on them). The use of disguised guns on auxiliary cruisers increased the risk inherent in stop-and-search rules, but the primary danger came from the wide-spread adoption of radio, which meant that a merchant could call for help as soon as a submarine appeared, even before it could issue its demands. Coupled with the rapidly-growing speed, range, and destructive power of combat aircraft, this technology ensured that complying with these rules would be suicide for any submarine.

For the first few weeks of the World War II the Kriegsmarine attempted to honour Germany's treaty obligations, but that attempt was in trouble almost immediately following the sinking of SS Athenia by U 30, and it was abandoned at end of November or the beginning of December 1939 with the issuing of War Order No. 154.

During the post war Nuremberg Trials, in evidence presented at the trial of Karl Dönitz on his orders to the U-boat fleet to breach the London Rules, Admiral Chester Nimitz stated that unrestricted submarine warfare was carried on in the Pacific Ocean by the United States from the first day that nation entered the war.^[1]

Since the introduction of long-range anti-ship missiles after World War II, which are able to destroy a ship from beyond the horizon, the London Rules are universally regarded as entirely void. It is indicative that despite the rules being used in the indictment of Dönitz, and although he was found guilty of breaching the 1936 Naval Protocol, his sentence was not assessed on the ground of his breaches of the international law of submarine warfare at the Nuremberg Trials.^[1]