(Australian Military Overview of this Tech.)

We are in Baghdad in 1991, and something strange is happening. A hush falls over the city as a huge shimmering face materialises in the sky. Soldiers and citizens prostrate themselves as each hears the voice of Allah, commanding them to overthrow the evil and treacherous Saddam Hussein. Within minutes an angry mob is storming the palace as the guards flee...

This highly imaginative scenario was proposed by US Air Force (USAF) planners for a bloodless victory in the Gulf conflict. The idea of putting words in God's mouth is not new. In the second century AD Lucian described a statue of the god Aesculapius that spoke to believers, aided by a hidden priest with a speaking tube.

The Baghdad plan involved projecting a giant hologram over Iraq. This kind of projection requires a mirror behind it. The scale of the project dictated a mirror several kilometres across up in space. So far the largest mirror developed has been 30 metres wide and present versions are too small to produce a convincing image at ground level.

Another approach would be to make a mirror out of thin air. When warm air lies on top of cold air, the difference in density is enough to bend light. At higher altitudes, a mirage can make whole landscapes appear in the sky. An artificial mirage could in theory be made by heating the atmosphere with radio waves or microwaves.

The military certainly appears to believe in the potential use of holograms. A USAF think-tank has devised uses ranging from deceptive holographic imaging to the Star Trek-sounding distortion field projector. These are described as useful for strategic deception purposes, particularly against an unsophisticated adversary. They would be projected by a special aircraft, an airborne hologram projector.

Perhaps the nearest current equivalent is the Commando Solo, a modified Hercules festooned with aerials and antennae and carrying pods of classified electronics. It can transmit across the electromagnetic spectrum, including radio and television signals.

The face of God needs a voice. A new technique using microwaves could produce this. When a high-power microwave pulse strikes the human body, a small temperature disturbance occurs, causing an expansion of tissue that can create an acoustic wave. A report from the USAF scientific advisory board says: "With a pulse stream, an internal acoustic field of 5-15KHz can be created which is audible. Thus it may be possible to 'talk' to adversaries in a way which would be most disturbing to them."

The practical difficulties in microwave transmission are formidable. The exact sound perceived depends on the size and shape of the hearer's skull and orientation to the source. Microwaves can be reflected or dampened by solid objects, so God's voice could have the underwater quality of poor radio reception. And would you believe in a God whose voice drops off when you walk behind a lamp-post?

But there were other problems with the plan. Images of Allah are forbidden in Islam. How can you project an image of God when nobody knows what He is supposed to look like?