It was a tactic that U.S. and British forces had planned to prevent, the torched oil policy of Saddam Hussein. But as coalition forces pushed into Iraq on Friday, the troops began to realize that Saddam's forces had not been completely stopped from setting fire to oil fields in southern Iraq.

Before the war began early Thursday, reports said special forces from the American and British armies had specific orders to secure Iraq's oil fields immediately after the conflict started. Their goal was to prevent a repeat of the environmental nightmare that Iraqi forces caused in Kuwait in 1991.

But U.S. Secretary of Defense Donald Rumsfeld acknowledged on Thursday that Iraqi forces had succeeded in setting "as many as three or four" oil wells ablaze in southern Iraq, near the Kuwaiti border. Published satellite images showed palls of thick, black smoke drifting west from the oil fields. By Friday, the number of reported fires had grown to 30, and black smoke was swirling through parts of Kuwait.

By Saturday, the number had been reduced. Iraq sabotaged only nine oil wells of about 500 in a southern area of Rumaila as U.S.-led forces invaded on Thursday, Gen. Vince Brooks said.

Oil fires turned day into night

The smoke drifting through Kuwait was a troubling reminder for people who experienced the first Gulf war. As the Iraqi army fled coalition forces in the last days of the conflict in 1991, Saddam ordered his troops to set oil wells on fire as they retreated from Kuwait, turning day into night. In all, 730 wells were detonated. Many others gushed oil, forming burning lakes of crude oil in the desert. Iraq also intentionally released 11 million barrels of oil into the Arabian Gulf from January to May 1991, contaminating more than 800 miles of Kuwaiti and Saudi Arabian coastline.

The financial implications arising from Saddam's scorched-earth campaign were colossal. The coastal clean-up alone cost more than €660.3 million ($700 million). Getting the well head fires under control took international firefighting crews almost two months. The total cost of firefighting effort and oil-well repairs has been put at more than €11 billion. The loss of so much oil also put a heavy dent in the Kuwaiti economy.

The environmental impact was disastrous. Mohammed al-Sarawi, chairman of Kuwait's Environment Public Authority, said the country's desert was still badly polluted. "We have about 20 million cubic meters of contaminated soil," he told BBC News. The contamination has played havoc with the fragile desert vegetation in these areas, he said. The marine environment -- particularly its coral reefs -- has still not recovered from the millions of barrels of oil the Iraqis pumped into the Gulf from Kuwait's oil terminals, he said.

Smoke clouds added to global warming

The dense smoke clouds from the Kuwaiti oil fires also created a barrier that prevented solar energy from reaching the surface of the Earth and stopped heat from escaping to space. Some scientists predicted significant global warming as a result of a 5 percent increase in emissions of carbon dioxide, a greenhouse gas.

The burning oil fields were also blamed for causing more widespread problems, none more contested than the claims that the acrid black smoke containing soot and petroleum mist was a major cause of Gulf War Syndrome, an assortment of maladies and illnesses experienced by many troops on their return. About 25,000 British and American troops have experienced symptoms of the syndrome, according to Medact, an international medical institute.

Gulf War Syndrome linked to toxic fumes

Exposure to air-borne petroleum droplets or "oil rain" can result in fatigue, skin rash, muscle and joint pain, headache, loss of memory, shortness of breath, and gastrointestinal problems. These later turned out to be the main symptoms of Gulf War Syndrome. However, there is no concrete proof that the burning oil fields contributed to the debilitating illnesses experienced by returning soldiers.

One of the units affected was the U.S. 11th Armored Calvary Regiment, which reported major symptoms among its troops when it returned to its Germany base on Sept. 20, 1991. The unit was stationed 48 to 130 kilometers (30 to 81 miles) from the oil field fires during a time of high winds that dispersed the smoke plume from the fires.

But a number of health risk assessment investigations at the time by the U.S. Army and the Environmental Hygiene Agency found no adverse risk to soldiers from the exposure to the atmosphere around the blazing oil fields.