Why did Jacques Chirac decide to conduct a final series of nuclear tests before signing France up for the Comprehensive Test Ban Treaty, knowing full well his stance would stir protest around the world? Yet again, it seems, France has singled itself out and-to judge by the commentaries one is now hearing-is embarking almost casually on this test track, as if the President of the Republic had yielded willy-nilly to the pressures of the nuclear lobby and to an incorrigible Gaullist fondness for grandeur. In fact, the decision to test stems from a long-term nuclear strategy that involves techno strategic, political and European considerations.

First, on the technology front, bombs are no more immune to entropy than anything else. The life cycle of France's existing thermonuclear weapons will end around the year 2015. At that point the choice will be either to relinquish the country's nuclear arsenal or to build new weapons. Common sense suggests that it would suffice to produce exact copies of current nuclear devices to maintain the deterrent. But the reality is rather more complex, for perfect clones cannot be manufactured a few years hence. Materials can change slightly, and the manufacturing techniques employed, such as soldering, evolve over time. When it comes to nuclear weapons, even small changes can have enormous consequences for reliability.

The essential aim of the tests is to validate our ability to produce so-called robust nuclear weapons that will retain their capability over a long period of time and to perfect simulation techniques that will make testing unnecessary. Obviously, it would have been preferable to have done all this a few years ago, as the U.S. did. However, the French government had different priorities and had not expected such an early Comprehensive Test Ban Treaty. That was an error of judgment in need of correcting with tests, for France must certainly preserve a functioning deterrent. Nobody knows what threats may loom in the next century. A glance at the global changes wrought since the end of the 1980s confirms that the unfolding of history springs many surprises.

Second, on the political level, France, a founder member of the nuclear club, must take account of the strategic reshuffle that has accompanied the vanishing of the Soviet Union. The new world order, supposedly ushered in by the defeat of Saddam Hussein by a U.S.-led coalition acting at the U.N.'s behest, has yet to prove itself. Witness the Bos nian debacle. In crisis situations the only players that matter are those who have taken the prior trouble and effort to organize their defense posture. France remains closely bound to the Atlantic alliance, but has never considered it the definitive and immutable answer to all likely predicaments, if only because it is always possible for assessments and interests to diverge across the Atlantic.

Last, and perhaps most important, France is steadfastly committed to the process of European integration. This will probably require several more decades and be successfully completed only when the European Union endows itself with an autonomous defense organization. It is felt in Paris that the day will come when French and British nuclear forces will form part of the bedrock of Europe's defense and that there is no incompatibility between this goal and a deepening of the Euro-American alliance. The issue has in fact been floated for at least 20 years, and now deserves closer attention than ever. It is also partly with European defense in mind that France has stuck against all odds to its efforts to develop a space industry capable of launching observation satellites and other payloads into orbit. The French have thought to involve their European partners in this endeavor, and this vision has come to be shared by a significant and growing portion of the German political establishment.

Toward the middle of the next century, the U.S. and the European Union will have to be the linchpins of a bipolar Western world. No less than this will be required to balance the immensity of a China committed to developing all aspects of its economic and military might, not to mention other centers of power that may emerge in Asia. One of the great lessons of the 20th century is that in the absence of perfect collective security mechanisms , global and regional power balances are necessary to deter aggression and ensure the peace.

The feelings stirred by the final series of French nuclear tests are understandable. But it must be realized that the timing to which France has had to resign itself seems so unfortunate because of a fundamentally auspicious development, namely progress toward a global test-ban regime that makes it impossible to postpone further the completion of the French program. The decision to finish this process, in any case, is cast in the framework of France's geopolitical outlook. That outlook is inherently debatable, as are all such constructs, but it is nonetheless carefully nurtured and deep-rooted in national history stretching for more than a millennium strewn with a fair share of tragedy.

Thierry de Montbrial is director and founder of the French Institute for International Relations .