A week of airstrikes, including the most concentrated precision hits in U.S. military history, has left tons of rubble and deep craters at hundreds of government buildings and military facilities around Iraq but has yielded little sign of a weakening in the regime's will to resist.

Early hopes that the thunderous power and shock effect of the bomb and missile attacks might topple Iraqi President Saddam Hussein have given way to more sober predictions of a longer-term war. Despite the air assault, mass surrenders of Iraqi troops have not occurred, and some military chain of command still appears to be functioning.

After hesitating to hit the government's broadcast facility and allowing state-run Iraqi TV to remain on the air, U.S. war planes struck it early today. News service journalists in Baghdad reported explosions and smoke in the vicinity of the Iraqi television building and the Information Ministry.

The signal from Iraqi Satellite TV, which broadcasts 24 hours a day outside Iraq, went off the air around 4:30 a.m. (8:30 p.m. EST Tuesday). Iraq's domestic TV service was not broadcasting at the time.

While other strikes in and around the Iraqi capital continued through the night, with Republican Guard buildings and intelligence centers also on the target list, the initial focus on clobbering Iraq's leadership was clearly widening to hitting Republican Guard forces in the field.

Military officials involved in the air campaign said one of their biggest surprises has been the lack of any challenge from Iraq's air force. Iraqi pilots had trained with some frequency before the war, at times taunting U.S. and British patrols by entering the "no fly" zones. But since the start of the fighting, not a single Iraqi aircraft has taken to the skies, the officials said.

They also reported the emergence over the past few days of a sizeable number of unexpected targets -- more than 300, by one officer's estimate -- mostly involving mobile air-defense radars or missile launchers being repositioned. But other priority targets that were on the initial target list have gone unstruck, officials said, largely out of concern for avoiding civilian casualties. In Baghdad, these have included the Ministry of Defense, the Rashid Hotel and, until today, the state-run television facilities.

Senior U.S. military officials said yesterday that the air campaign has unfolded according to plan, and they continued to express confidence in the toll the strikes were taking. Defense Secretary Donald H. Rumsfeld said he and other senior Pentagon officials had never expected the war to be over in a few days, noting that his view has consistently been that the length was impossible to predict with any certainty.

"Why would we have put in train the hundreds of thousands of people to go do this task if we thought it was going to be over in five minutes?" he said at a Pentagon news conference.

But as recently as March 4, in a breakfast with reporters, Air Force Gen. Richard B. Myers, chairman of the Joint Chiefs of Staff, described the war plan as intended to shock the Iraqi leadership into quick submission with an opening assault much different from that of the 43-day 1991 Persian Gulf War.

"If asked to go into conflict in Iraq, what you'd like to do is have it be a short conflict," Myers said at the time. "The best way to do that would be to have such a shock on the system that the Iraqi regime would have to assume early on the end was inevitable."

Reminded yesterday about those remarks, Myers said he had not meant to imply any specific timeline. But he also warned that the Iraqis will "have a lot more to be concerned about shortly," noting the arrival of a U.S. Army division on the outskirts of Baghdad.

The opening assault on Iraq contained a mix of near-simultaneous air and ground operations on a scale and with a complexity never before attempted by U.S. commanders. It was the combined effect of these actions -- airstrikes from above, ground invasion from the south and Special Operations actions throughout the country aimed at thwarting the use of chemical or biological weapons -- that was supposed to produce the "shock and awe" sufficient to bring down the Iraqi leadership.

The aerial bombardment was to be the most dramatic element in this mix, delivering strikes so precise and extensive that Hussein and senior aides would see little choice but to surrender. During the first intensive salvos Friday night, U.S. munitions tore into presidential palaces, intelligence headquarters and Republican Guard buildings in Baghdad and in Hussein's hometown of Tikrit, north of Baghdad, as well as into command posts, communications facilities, airfields and air defense sites elsewhere. The number of such attacks has dwindled since then, although 30 heavy explosions were reported in Baghdad shortly before dawn today.

Increasingly, U.S. and British warplanes have turned to supporting ground operations and striking Republican Guard forces in what the Pentagon terms "kill boxes," zones in which pilots are authorized to search for and attack targets at will. While such attacks were hampered yesterday by dust storms, Myers said that in the previous two days, roughly half the strike missions had focused on Republican Guard forces.

To underscore U.S. claims of precision, briefers at the Pentagon and at the Central Command field headquarters in Qatar have displayed before-and-after photos of several of high-priority sites that were stuck, including compounds belonging to the intelligence service, the palace guard and the Special Security Organization. The pictures showed crumbled barracks and cratered buildings, while nearby walls and neighborhoods remained intact.

In one image yesterday, a building said to have hidden short-range ballistic missiles in northwest Iraq was shown leveled right next to a water treatment plant that appeared unscathed.

But while confident about their ability to strike with precision, U.S. military officials have opted to skip some targets in the interest of avoiding civilian casualties.

"It's always a balance, you know," Myers said on ABC's "Good Morning America." In some cases, he added, U.S. commanders have accepted "a little bit more risk" to their forces rather "than to bring the population in harm's way."

Another senior official said the hit list has concentrated on leadership and military targets, excluding electrical power, water, telephone and other facilities that provide critical civilian services and will factor significantly in reconstructing post-war Iraq. Bridges have been hit "only sparingly," the official said. An attack Monday on a bridge in western Iraq ended up mistakenly striking a bus carrying Syrian civilians, killing at least five people.

While U.S. and British warplanes have not encountered Iraqi military aircraft, they have run into Iraqi efforts to jam the guidance systems of bombs that depend on signals from Global Positioning System (GPS) satellites.

"We've been able to identify the location of each of those jammers, and I'm happy to report that we have destroyed all six of those jammers in the last two nights' airstrikes," Air Force Maj. Gen. Victor Renuart, director of operations for the Central Command, said at a briefing in Qatar. He said the devices had had "no effect" on U.S. military operations.

At the Pentagon later in the day, Myers showed video footage of an F-117 jet using a satellite-guided weapon to take out what he said was the last GPS jammer that U.S. troops had been able to find. While Myers did not say so explicitly, the GPS jammers appeared to be among the equipment the Bush administration alleges was sold by Russia to Iraq.

Officials declined to provide estimates of Iraqi casualties or the extent of damage done to Republican Guard troops so far, except to say that U.S. and British planes have destroyed a substantial number of tanks, armored personnel carriers and artillery pieces.

"I think what you'll see in the end is that many of those tank revetments are filled with junk right now," Renuart said.

Iraqi children walk through the rubble of a Baghdad building that authorities say was destroyed by an airstrike.