Iraq's use of phony Scud missile launchers to fool allied fliers is part of a military strategy that goes back to the days of the Trojan Horse.

Through the centuries armies have done a delicate dance of veils to convince enemies they were weaker, stronger or somewhere else."This kind of deception goes back a long way," said Steven Kosiak, a research analyst with the Center for Defense Information in Washington. "In this war, it will be a question of how clever both sides are."

Round One may have gone to Saddam Hussein. U.S. officials have acknowledged Iraqis have used plywood - perhaps even cardboard - mockups of the missile launchers to mislead the determined hunt for Iraqi Scuds.

"They do use decoys and they use them well," Lt. Gen. Tom Kelly, director of operations for the Joint Chiefs of Staff, said at a briefing earlier this week.

Kosiak said the Iraqi tactic is no surprise.

"Iraq draws a lot of military doctrine from the Soviets," he said. "They used those tactics in World War II. They would dig fake bunkers and make tanks out of wood to draw fire."

The Iraqi use of Scud decoys raises questions about other targets in the allies' relentless air war.

Tank emplacements, bunkers and other positions believed to be held by the vaunted Republican Guard may be empty, diverting tons of expensive smart bombs and rockets away from real targets.

"To be effective, it doesn't always have to fool people. It just has to raise questions," Kosiak said.

Decoys will not turn the course of the war, but they mean the allies will have to spend more time on reconnaissance and more money on wasted weapons.

"It may mean the air war will take a little longer," Kosiak said.

Armies have been raising these questions since ancient times, pitching empty tents and burning scattered campfires to fool enemies about their size and strength.

During World War II, the English set fires on an empty island to lure German Luftwaffe bombers away from Portsmouth. Extensive army camps, empty but for a few radio operators, were established throughout England to convince Hitler that phantom armies were preparing to invade Europe through Norway.

Advanced weapons may be useful in countering Iraqi tricks. Radar and infrared sets aboard many U.S. fighters, helicopters and tanks can "paint" a target and judge if it is a "cold" inanimate object made of plywood or a real tank whose engine creates a heat signature in the gun sight.