"I love Germany so much," wrote the French novelist Francois Mauriac, "that I am glad there are two of them." That phrase is cited with increasing frequency these days, but the sentiment is old. Clemenceau expressed it first as he wistfully reflected on the delicate balance of power nurtured in the 19th century by Austria's Prince Metternich. Since World War II the division of Germany has been central both to the tensions of the cold war and to the stability of the cold peace that accompanied it.
Throughout this period West Germany's allies paid facile allegiance to the goal of reunification,...