At the beginning of World War II U-Boats were required to follow the rules set out in the London Submarine Agreement of 1936. (These rules were also supposedly applicable to all beligerents.) These rules included:

The U-Boat was required to surface and challenge a merchant vessel before it could attack it.

The U-Boat was to send a boarding party and inspect the vessel to determine if it was a legal target.

If it was determined that the ship could be sunk, the U-Boat had to insure the safety of the ship\'s crew first. Lifeboats were not considered adequate on the high seas, so the U-boat would be required to take the crew aboard.

Just these conditions make it obvious that the rules were logically only applicable to surface warships and raiders, which had room for a large number of prisoners. However, there were conditions which exempted the U-boat from the inspection requirements, including:

Any merchantman escorted by an enemy warship or aeroplane.

Any merchantman that attempted to resist when challenged.

Troop transports, since they were regarded as warships.

A merchantman using its wireless to report being stopped was also considered a hostile act. (The British imposed a requirement that merchantmen do just this well before the war actually began.)

Since the British almost immediately armed their merchant vessels, and quickly organised them into convoys, much of the effect of these rules was negated. Sheer practicality also prevented some compliance.

Germany did make an effort, however brief, to follow the Prize Rules. In the Pacific, the United States ignored them from the beginning of the war. Nor were the British particularly scrupulous in this area. The truth is, of course, that a submarine is simply too vulnerable and underarmed -- not to mention too small -- to follow rules which were really an extension of rules originally intended for surface warships. Unrestricted submarine warfare was the rule on all sides from very early in the war.

J.T. McDaniel