[MRM]

Tabs' discussion of unrestricted warfare against the Japanese sub fleet notwithstanding, i'll share an anecdote from D-Day that I find telling. I believe it comes from the book The Longest Day. The Americans landed on the beach, fought their way on shore, and soon found themselves fighting on the farms of Normandy. One group was coming under serious fire (which of them wasn't) and were rushing to set up some artillery to take the heat off. The best place to set up was a farmer's yard. A soldier was dispatched to the famer's house to ask permission to set up. The farmer, used to years of Nazi occupation, laughed bitterly and gave permission to set up. As the US soldier turned to go the farmer asked sarcastically what the Americans would have done if he said no. The GI turned back to him in suprise and said "We'd go somewhere else, of course." That's the military of the country I grew up thinking I belonged to.

As for the issue of unrestricted warfare on the Japanese merchant ships. There was a difference between those attacks and the German equivilent that makes all the difference in the rules of war. The Japanese were fighting a war of aggression and the merchant fleet was working in direct support of that war. As such, all Japanese merchant vessels were legitimate targets of war. The Allied merchant fleet was not in the same position. Not only was the Allied involvement in WWII not in support of a war of aggression and not all merchant shipping was done in support of the war effort. Therefore, not all Allied shipping were legitimate targets of war. In other words, the campaign against Japan's merchant fleet saved Japanese, as well as American lives.

As a side note, the US sub campaign was so effective that it starved Japan of crucial materials and stopped reinforcements to the point that it shortened the war, saving untold lives. The question of whether the US would have had to invade Japan or just wait until it was starved into submission is still debated, but the effectiveness of the attacks on merchant shipping set the stage for Japan's surrender after the atom bombs were dropped.