FERRARA, Italy -- The tension between Germany and Italy, unleashed in recent days by the incautious words of Stefano Stefani, our tourism minister, has played out since ancient times. Long before Mr. Stefani, who resigned on Friday, accused German tourists of invading Italy's beaches and conducting burping contests, there has existed an ambivalent relationship of attraction and repulsion between our countries. Though this dynamic has stimulated culture, it has also brought about disquieting, even disastrous, political outcomes. It all began with Rome under the emperor Augustus, when Varus's Roman legions were exterminated by the German forces under Arminius in 9...