When a small, broke, pariah state in southeast Europe takes on the most powerful military alliance in world history, it naturally resorts to every ruse in its military manual.
Sometimes, military sources at NATO headquarters say, the tricks are simple but effective: cardboard cutouts of tanks, dummy planes, and other decoys to fool pilots into thinking they have destroyed more than they really have.
Sometimes they are more high-tech, such as the Army command's use of standard cell phones to stay in touch with the troops when NATO bombs destroy their radio links.
But the way the Serbian forces have ducked and dodged and held together is a reminder that the Yugoslav military, descended from an anti-Nazi guerrilla army, had always planned dogged resistance to the overwhelming air power of an invading enemy - only they expected the enemy to be the Soviets.
Serbian commanders also had plenty of time to study NATO habits in Bosnia, and time to hide many of their assets in the first, relatively quiet, few days of the war.
"They have been very clever in their ability to conceal themselves," says a senior NATO diplomat.
That means that many Serbian weapons systems are simply hidden somewhere and switched off, so as not to emit the electromagnetic signals that NATO planes can detect.
It means that the Yugoslav Air Force has repositioned some of its planes near straight stretches of road that can be used as runways.
It means that ammunition has been taken out of easily identified bunkers and stored in the woods.
It means too that Serbian soldiers are parking their tanks and artillery near civilian homes or mosques, knowing that NATO pilots will not attack them for fear of "collateral damage."
Though major roads and railways have been destroyed, there is always another way around; though fuel dumps have been hit, the Yugoslav Army, like NATO armies, is assumed to have stockpiled enough diesel to fight for three to six months.
With Army headquarters located in caves or specially dug hardened bunkers in the mountainsides, and a network of thousands of radio transmitters and relay stations, "their command and control capability remains pretty robust," the senior NATO diplomat acknowledges.