The Berlin Wall was quite literally the prop on which the entire Soviet security structure for Europe rested. When it fell, Moscow's continuing illusions that Eastern Europe could somehow be maintained as a belt of neutral states separating the Russian heartland from the West collapsed like a house of cards.
And yet the edifice had appeared so solid, so permanent. In the euphoria that followed the fall of the Wall -- and which was again on display during the 20th anniversary celebrations -- we forget that prior to 1989, the division of Europe into two blocs, East and West, was seen as a permanent feature of the international order.
America's own security architecture throughout the Pacific Ocean basin may now be based on similarly impermanent divisions in Asia. Take, for instance, the utility of North Korea. South Koreans and Japanese may question the value of their ties to Washington from time to time. But all it takes is one incident -- for instance, the naval clash earlier this month in the Yellow Sea between North and South Korean vessels -- for statesmen in both Seoul and Tokyo to reaffirm their alliance with the United States. But if one day the barbed wire and landmines of the DMZ are parted and Korea starts down its path to unification, will that rationale still apply?