Today's U.S. attack on a residence on the outskirts of Baghdad was an unscripted effort to decapitate Saddam Hussein's government. But the unsuccessful strike showed just how difficult that will be.

There was no definitive word from U.S. officials late Wednesday that Hussein was among the "senior elements of the Iraqi leadership" that U.S. officials said were the target.

But war planners and military targeting experts have been crossing their fingers that they might be presented with the chance to eliminate Hussein or other leaders with an airstrike that could effectively end the war before it had really begun.

Targeting teams have spent months combing through intelligence on Iraq to pick palaces, bunkers and other facilities where Hussein might take cover. But until late Wednesday, this silver-bullet scenario was regarded as an extreme longshot.

Officials familiar with the war plans had said Wednesday that although the aerial campaign would certainly include targets where Hussein might be hit, the plans discounted this possibility and instead focused on paving the way for his overthrow.

One senior Air Force officer said the air plan for Iraq is essentially an intensified version of the 1998 Desert Fox campaign ordered by President Clinton. That four-day assault sought to undermine Hussein by bombing barracks, command posts and other facilities of the security forces most directly responsible for protecting him.

The aim, the Air Force official said, is to crack the protective shell around Hussein and create opportunities for members of his own regime to carry out a coup.

U.S. military and intelligence officials say that Hussein is an amazingly elusive figure and that the United States rarely gets even a glimpse of when he moves, where he hides and how he communicates.

"I don't think anybody's ever had a good idea of where he is at any given moment, or where he will be in the future," one military intelligence official said Wednesday before the surprise attacks. "I don't think you'll ever have good information on that."

Recent history has given U.S. officials reason to be pessimistic. The United States has been able to overwhelm enemy forces with dazzling military power but has struggled or failed to catch or kill individual leaders, from Libyan President Moammar Kadafi to Al Qaeda leader Osama bin Laden.

Seeking to dampen expectations of quick success against Hussein, Pentagon officials have repeatedly stressed that the stated objectives of the war are "regime change" in Iraq and the elimination of its weapons of mass destruction.

Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, recently told reporters that victory in the war would be defined by disarming Iraq, not eliminating Hussein.

But other officials, Pentagon advisors and commanders of the 1991 Persian Gulf War have said there is no question that the United States would seize any opportunity to end the war early with an airstrike on Hussein.

In fact, the United States attacked a vehicle in the 1991 war based on intelligence that it was one Hussein routinely used, only to learn later that Hussein's security forces managed a small fleet of such vehicles and that the Iraqi leader escaped unharmed.

"We tried to smoke him. We didn't get him," said a former senior intelligence official.

U.S. officials also hoped to hit Hussein in the 1998 strikes after U.N. weapons inspectors were withdrawn.

Hussein has surrounded himself with layers of security. He is believed to employ several look-alikes as decoys. His movements are hidden even from his most senior advisors, and he rarely stays in one location more than a night or two.

Hussein has also spent a fortune building palaces and an elaborate network of tunnels under Baghdad, as well as bunkers that are believed to be impenetrable to all but the most potent U.S. bombs.

The closest the United States has come to penetrating Hussein's inner circle may have been in the late 1990s, when U.S. spy agencies took advantage of the weapons inspection programs to install sensors and listening devices.