In the recent Hollywood conspiracy theory movie Enemy of the State, the CIA is portrayed as the all-seeing eye - the secret service with spooks around almost every corner - and satellite images of its enemies' every move.

Nato's accidental bombing of the Chinese embassy in Belgrade has served as a reminder that real war is not as smooth and slick as Hollywood - and the alliance's laser-guided bombs are only as good as the intelligence which pinpoints the targets.

Nato says the conflict aims to minimise civilians deaths - but questions are being asked about how it chooses targets.

Jamie Shea, Nato's spokesman said the alliance's own investigation into the embassy bombing had put "the error in the intelligence apparatus".

An unusual joint CIA-US Department of Defense statement admitted poor information had led to the attack on the embassy rather than the Yugoslav Federal Directorate of Supply and Procurement 200 yards away.

But it added: "The extensive process used to select and validate targets did not correct this original error.

"A review of our procedures has convinced us that this was an anomaly that is unlikely to occur again.

Steps to engagement

BBC Defence Correspondent Jonathan Marcus: "Questions are being asked about US intelligence operations"

The process which leads from a military boardroom to a pilot releasing a weapon is highly technical - perhaps conducted in this case without the aid of the Belgrade telephone directory or tourism map, both of which list the embassy's address.

As an alliance representing 19 countries, Nato employs a chain of command which ensures that all members agree a course of action.

The process begins in the shadows of the intelligence community.

Its work can be carried out in a variety of ways including agents on the ground to the use of imaging satellites orbiting above theatres of conflict.

Earlier in the conflict, there was speculation, predominantly in the US media, that military agents had contacted the Kosovo Liberation Army for help in targeting Yugoslav units in the province. The alliance declined to comment.

There has also been speculation in the UK press that the British army's elite SAS units are or have been behind enemy lines.

What Nato has been keen to show off is the might of the US's satellite and air reconnaissance - the hardware which ultimately provides the co-ordinates for guided weapons.

These images have played an important role in the media war, with Nato briefings displaying images of alleged mass graves and burnt-out villages in Kosovo.

Political guidelines

Military planners, working under strict political guidelines, scrutinise the lists and select and grade the targets in line with current mission parameters.

Former CIA agent David Whipple explains problems with the intelligence

How much freedom the planners actually have is a grey area dominated by the conflicting requirements of military strategy and political concerns.

Earlier in the conflict, General Wesley Clark, Nato's supreme commander in Europe, was under orders to limit strikes to purely military targets.

But his analysts now have authority to draw up lists including infrastructure which has both a civilian and military use.

Military leaders and Nato political representatives at Nato's Brussels headquarters then review the proposed targets and firepower needed before seeking final approval - another grey area subject to domestic agendas and the need to wage war by consensus.

Gen Clark has authority to approve targets in the majority of cases - but must seek political approval where targets are deemed likely to inflict suffering to civilians or cause "collateral damage".

Since US forces are conducting the majority of strikes, President Bill Clinton is has the final say for highly sensitive attacks.

In the UK, Defence Secretary George Robertson approves lists with the attorney general John Morris and the involvement of the prime minister if required.

Defence Analyst Wing Commander Andrew Brookes said: "The military will produce a long list of targets that they wish to attack.

"That list will be prioritised and presented to politicians and will have to be accepted according to how they see the risk."

Regrets

All of which means that both military and political leaders approved the Chinese embassy attack.

Irrespective of the quality of the intelligence, the alliance's leaders say there is one fact that cannot be overlooked.

Nato deeply regrets ...

"There is no such thing as clean combat," said Pentagon spokesman Kenneth Bacon.

"We have the best pilots in the world. We have the best weapons in the world. We have the best-planned missions.