THEIR side-by-side deployment in Bosnia is the first such cooperation for Russian and American soldiers ''since we met at the Elbe,'' in the final months of World War II, as one US officer puts it.
Russians and Americans have been holding joint military exercises for a couple of years now as part of NATO's Partnership for Peace program.
But this real-life operation provides the former cold-war foes a chance to put a little warmth into their relationship. It shows that when the politicians are ready to cooperate, the troops on the ground are ready to follow.
About 1,500 Russian troops are taking over 16 checkpoints under the command of the US division of NATO troops based at Tuzla.
The Russians and Americans will be patrolling alongside each other and exchanging information, notably on minefields, says Sr. Lt. Leonid Fedyaev. They will be performing the full range of ''peace enforcement'' activities.
''This is the opportunity of a lifetime.... I'm the first one in my family to meet a Russian,'' says Sgt. Scott Baier of Schenectady, N.Y.
The personal interaction with the Russians strikes him, he says, as ''one of the best things'' about the assignment in Bosnia.
This mission will include using some big guns, too, if necessary. Capt. Glenn Hedin of Ohio, part of a field artillery liaison team, says, ''We came here prepared to do whatever it takes. If that means fighting, so be it.''
Accordingly, he will be exchanging information with the Russians on targets, ammunition, and location of equipment belonging to NATO troops, as well as that of the former warring factions.
Officers and enlisted men of both nations here at the Russian headquarters in Bosnia are overwhelmingly upbeat about their prospects for success. They repeatedly stress the key elements they see at work: Military professionalism; clarity in the political decisionmaking behind NATO's Implementation Force (IFOR), and the trust and personal relationships they say are already developing.
Russia is not putting its IFOR troops directly under NATO command, but rather under the command of the US 1st Armored Division. The Russian sector is a subset of the American sector in northeastern Bosnia. Progress of the Russian deployment, like that of other aspects of IFOR and the Dayton accord, has been basically smooth although somewhat behind schedule.
But the Russian presence within IFOR is expected to hold off some of the risk of escalation. Maj. Randolph Ponder of West Hills, Calif., says that having the Russians in IFOR will make for a better enforcement of the accord ''because the Serb population will feel the force is evenhanded.''
But Lieutenant Fedyaev insists, ''The Russian troops must be objective - they can't favor one side or another. The Russians have been considered allies of the Serbs, and Americans allies of the Muslims, but with this mission we can't have that.''
Russia's success within IFOR could have European security implications far beyond the Balkans. With the cold war over, defense experts say Europe needs a new ''security architecture.'' The former Warsaw Pact countries, wary of a destabilizing power vacuum, want to join NATO.
But unless NATO can establish a constructive new relationship with Russia, NATO enlargement could well amount to merely ringing down a new Iron Curtain farther east. IFOR has been widely hailed as a significant opportunity for Russia and NATO to develop just such a relationship.
If IFOR represents the new face of European security, it is a very youthful face. Many of the Russian soldiers chowing down in the base mess hall could be students in a high school lunchroom.
Russian Pvt. Andrei Sivkov asked whether he ever considered the Americans his enemies, responds, ''No, because I was too little.''
Similarly, Maj. John Bushyhead, plans officer with the First Armored Division, just back from a tour of the Russians' camps, speaks of ''the relationship we've built'' with his Russian counterparts and the ''walls of suspicion'' that are coming down.
Asked what all this might mean for possible NATO enlargement and other security issues, however, he responds, ''We've got to get through Bosnia first. If we can't do this there's not much hope.''