The most important and successful relationship the United States has ever had with other nations is now headed for inevitable sweeping change.
For 50 years NATO has been a simple club, with simple rules: mutual Western defense against a threat from the east. But the terms of the security partnership struck between NATO and Russia this week mean that the old club's simple mission and ways of doing business no longer apply.
Now the old adversary is an emerging democracy and has a voice - not a veto - in alliance affairs. Soon club meetings will be bigger, as the West will likely offer NATO membership to Eastern European states that have long pounded on its door.
Will a larger, more complicated NATO lose focus and effectiveness? Or does this modernization reflect the needs and complexity of the post-cold war world?
"All of us are trying to change ... the whole pattern of thought which has dominated the international politics of Europe for 50 years," said President Clinton Tuesday as he hailed the NATO-Russia deal.
For many US citizens the word most closely associated with NATO may be "somnolence." Unlike taxes or Social Security it's not something whose impact on their life is immediately apparent.
But it's arguably the most fateful issue that the US government will deal with this year. Consider this chain of events: the NATO-Russia deal is intended to set the stage for the official beginning of NATO enlargement later this summer. Deserving candidates - most likely Poland, Hungary, and the Czech Republic - will probably be offered membership in July.
And if NATO expands, US troops, weapons, and nuclear warheads will be officially pledged to defend an area of Middle Europe. At a time when US public opinion may be in favor of a focus on domestic problems, the country may be profoundly expanding its role in the world.
European leaders used to worry the US wouldn't want to defend Bonn. Now they'll wonder the same thing about Bucharest.
Senate approval of NATO expansion isn't expected to be easy. Many experts say it will make the Clinton administration's recent struggle to win ratification of the Chemical Weapons Treaty look like a stroll in Lafyette Square.
US commitments won't be the only Senate issue. Cost will be a problem as well.
"There's no threat, and yet you're asking for increased spending in NATO," Sen. John Warner (R) of Virginia lectured Secretary of State Madeleine Albright in a hearing last month. "I do not see the staying power of the country behind that decision," said Sen. Warner. "I do not think America wants to foot that bill."
Clinton officials argue in return that the process they have begun is successfully threading a difficult needle. On the one hand, they say, the new deal with Russia will help ease Kremlin concerns that a new, expanded NATO is aimed at them and will threaten their security. And on the other hand, officials argue, NATO expansion will spread stability to a part of Europe too many soldiers have trod this century, and ease Eastern European concerns about exclusion from the benefits of the West.
In essence, the US is trying to avoid repeating the mistakes of two big treaties that shaped the twentieth century, say officials. The US doesn't want another Yalta, which in 1945 allowed the Soviet Union to swallow up large sections of European territory. But neither does it want another Versailles - a 1919 pact whose harsh treatment of a supine Germany bred resentment that helped lead to World War II.
If nothing else, this week's actions could provide the Clinton administration with some political bragging points. NATO expansion is one of the White House's top foreign policy priorities, and failure to strike a NATO partnership with Russia would have led to sniping from foreign policy critics that a tired President was going nowhere in his second term.
But now Mr. Clinton has a foreign success on a par with his recent balanced budget deal. Perhaps carried away in the moment, Clinton talked about NATO this week with rhetoric that was expansive even by his standards. "It is possible to enlarge NATO, to maintain its effectiveness as the most successful defense alliance in history, to strengthen our partnership with Russia, and to do all this in a way that advances our common objectives of freedom and human rights and peace and prosperity," said Clinton Tuesday.
Some prominent US foreign policy experts have long begged to differ. George Kennan, a retired diplomat who was instrumental in shaping US policy towards the Soviet Union in the wake of the cold war, argues that NATO expansion is an attempt to fix something that isn't broken and could be a "fateful error".
Nor are the other current NATO members as enthusiastic about this process as is the US. But by going along with Washington, Bonn and other European capitols win a continued - indeed, an expanded - US commitment to their part of the world. And perhaps not incidentally, the plum of NATO membership may lessen Eastern European pleas for inclusion in the economic-oriented European Union.