AS the world focuses on the massive NATO-led force that has just set up in Bosnia, it may be worth pausing for a moment to consider if and under what circumstances that force is going to get out.
There are only three main possibilities: a calm and orderly withdrawal within a year as planned, a disorderly withdrawal under hostile conditions, or a decision to maintain some sort of peacekeeping force.
To avoid a potentially acrimonious debate among NATO allies over these options, it would be useful for European and American leaders to agree now on what will happen when it is ostensibly time to leave. If they do not do so, what should be a private, internal negotiation among allies will likely be a very public row, possibly with disastrous consequences.
The first withdrawal alternative - with IFOR, the peace-implementation force, coming out within a year, after Bosnia-Herzegovina has been put back together - is clearly the most desirable option, but it rests on the unlikely premise that parties to a conflict who needed a major combat operation to keep them apart in December 1995 will be living peacefully alongside each other by December 1996. A total, on-time withdrawal is a nice hope but is not likely, and certainly nothing to count on as alliance leaders are doing.
The second possibility - chaotic retreat under fire if the cease-fire breaks down - would also resolve the dilemma of how IFOR leaves, but the damage done to NATO's credibility, to say nothing of peace prospects in Bosnia, would be catastrophic. That realistically leaves the third option - IFOR or some part of it staying on longer than planned.
But just who will stay on? The United Nations has neither the troops, the money, nor the credibility with the parties to take over for the NATO force. The United States has vowed that its forces will not stay for more than a year. This was a prerequisite for the Clinton administration's willingness to contribute troops in the first place, and it was a key condition of the timid support expressed by the Senate in late December 1995. Europe, in turn, said it would not participate in the implementation force unless the US did and that its troops will not stay ''one day longer'' than the Americans, in the words of French Foreign Minister Herve de Charette.
A game of ''chicken'' is clearly shaping up that has the potential to destroy the progress made in patching up transatlantic relations through US participation in IFOR. In the heat of the coming election campaign, President Clinton may well declare the success of the US part of the mission and announce his intention to have all the troops home for Christmas as planned. European leaders would then insist that they will not carry the burden of Bosnia alone and that ''if you go, we go.''
Both sides will want to avoid two undesirable alternatives: committing to stay indefinitely in the Balkans, or abandoning a still-fragile peace and thereby possibly allowing the former Yugoslavia to plunge back into civil war.
If such a game of ''chicken'' must be played, the US would be likely to ''win.'' If Mr. Clinton determines that staying on would either cost him the White House or lead to a potentially indefinite commitment, he is likely to bring the troops home as planned. Failing to do so would be a gift to his critics, who would accuse the president of getting sucked into an unwise commitment and tying up large amounts of US troops and money in an area not of vital national interest to the US.
THE Europeans might well also threaten to withdraw, but the Americans could call their bluff. Would Europeans - with a combined GNP greater than that of the United States, nearly 700,000 men under arms, and hardly any global military responsibilities - really be so weak and disorganized that they could not manage the continuation of a Bosnian peacekeeping operation? All in a year when they were supposed to be constructing a much-ballyhooed common foreign and security policy?
If so, plenty of Americans will be prepared to return to their previous attitude that Bosnia is a ''European problem.'' Even if ''successful,'' the IFOR deployment is unlikely to be very popular in the US after a year of expenses and possible casualties.
To avoid a damaging public feud over a Bosnia withdrawal, the alliance should start working now on a concrete agreement for IFOR after next year. Ideally, the Europeans would stay on in some peacekeeping capacity, not as the result of a US ultimatum, but as part of a deal in which the Americans provide full logistics, intelligence, command, and air support for a reduced, but continued, peacekeeping operation. The US might even leave in up to 5,000 troops as a symbol of continued commitment.
Europe, in turn, would see the new IFOR not as a curse but as an opportunity to show that it can indeed manage a security operation on its own doorstep, with an appointed high representative, in tight coordination with the national capitals, representing the common interests of the European Union.
Europeans are resentful about the US hijacking of the peace process in Dayton, which left the impression that Europe is incompetent and only the Americans can run the show. But if Europeans are unable to work out a leading role for themselves in Bosnia with US support rather than domination, what other conclusion can be drawn?