IN HARM'S WAY

IT SEEMS CERTAIN TO BE A WHITE Christmas; snow already covers the ground in Tuzla. But merry? The weather will be bitingly cold, the air filled with the stench of diesel fumes. Christmas dinner will be the T-rations detested by G.I.s; carols will be sung to the hum of noisy electric generators. And many of the soldiers setting up camps for the Bosnia peacekeeping operation will sleep in tents. Big ones with wooden floors, heat, fluorescent lights and flush toilets. But still tents.

At the Tuzla airfield, ground crews will have little time to gripe. The former Yugoslav airstrip for fighter planes has only one runway, on which the outlines of filled-in holes created by Serb shelling can still be plainly seen. No matter: plans call for a U.S. cargo plane to land there every 20 minutes all day and eventually through the night. And only three planes can be on the ground at any time. Can this ambitious schedule be met?

Speaking by telephone from a bullet-pocked control tower, Air Force Colonel Neal Patton, who has been in charge of installing runway lights and precision navigation equipment and otherwise getting the field ready, expresses confidence that it can handle the planned traffic. But he adds, with a laugh, "We're going to go to church to pray for better weather." Snow and low ceilings last week caused several flights either to be held on the ground at the Ramstein air base in Germany or to circle Tuzla fruitlessly and go back, unable to land. The miserable conditions do have their bright side, however. "There's nothing like sunshine for a good firefight," says Marine Lieut. General Anthony Zinni, "and this kind of weather discourages that."

In a sense, the frenzied activity at the air base will be misleading. Fewer than 1,000 of the 20,000 American peace enforcers will be encamped around Tuzla by Christmas. Many others will be aboard trains rumbling through Austria and the Czech Republic en route to jumping-off points in Hungary, from which they will advance 50-odd miles across Croatia into Bosnia and Herzegovina. Others will still be at bases in Germany, waiting their turn to board the trains; some may not leave until February. Army commanders strongly deny, however, that the buildup is slipping behind schedule. Says Colonel Mike Sullivan, chief spokesman for the U.S. Army, Europe: "Slow and gradual is exactly where we want to be. This is a very deliberate, precise process in vicious weather on a very unfavorable terrain, and we're very aware of that. We're not going to expose soldiers and their equipment to this until we're absolutely ready."

Just getting into Bosnia is no easy job. The bridges across the Sava River between Croatia and Bosnia have either been destroyed by artillery fire or are shaky. So Army engineers will build two "float" bridges of steel, aluminum and Styrofoam; by Christmas, the spans should be ready for tanks to rumble across them. It will be quite a sight. The bridges will settle six to eight inches under the weight of the tanks, and water will come up above their tracks. It will look as if the tanks are gliding across on top of the currents.