From Hathway and Shapiro (2017):
The Allies supervised the drafting of new constitutions for each of the Axis powers and enshrined the prohibition on war into each state’s own governing documents. Article 26 of Germany’s Basic Law provided that “Acts tending to and undertaken with intent to disturb the peaceful relations between nations, especially to prepare for a war of aggression, shall be unconstitutional. They shall be made a criminal offense.” Article 9 of Japan’s new constitution provided that “the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as a means of settling international disputes.” Article 11 of the Italian constitution provided that Italy “rejects war as an instrument of aggression against the freedom of other peoples and as a means for settling international disputes.”
Why was the wording in Japan's constitution so much stronger and less ambiguous than Germany's or Italy's?
For convenience, the three phrasing pulled out in block quotes:
- Germany, Art. 26.1 GG
Acts tending to and undertaken with intent to disturb the peaceful relations between nations, especially to prepare for a war of aggression, shall be unconstitutional. They shall be made a criminal offense.
- Japan:
the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as a means of settling international disputes.
- Italy:
rejects war as an instrument of aggression against the freedom of other peoples and as a means for settling international disputes.
The above is not intended to be a replacement for the full quote from Hathaway and Shapiro, which I firmly believe should remain in the body of this question.