WASHINGTON -- U.S. and British air and naval forces attacked 50 separate Iraqi military targets Dec. 16 in the opening volley of Operation Desert Fox, Pentagon leaders said here.

As air strikes continued into the second day, Defense Secretary William S. Cohen and Army Gen. Hugh Shelton, chairman of the Joint Chiefs of Staff, briefed Pentagon reporters. Desert Fox, they said, was diminishing Saddam Hussein's ability to attack his neighbors either conventionally or with weapons of mass destruction.

"Last night's actions principally involved naval forces in the Gulf, with more than 70 Navy and Marine Corps strike and strike support aircraft from the USS Enterprise and well over 200 Tomahawk cruise missiles launched from Navy ships," Shelton said.

Missiles hit weapons of mass destruction sites, security sites and forces, integrated air defense and airfields, and the command and control infrastructure that supports Saddam's military and his regime, Shelton said.

Cohen stressed that the attack was aimed at military targets, not the Iraqi people. "We have no desire to increase the suffering Saddam Hussein has imposed on his people," the secretary said.

Although Shelton said no detailed damage assessment was available at that moment, he presented examples of successful strikes. He showed before and after photographs of two facilities in Baghdad, the Iraqi capital.

The first, a military intelligence center, provided information that helped Iraqi officials obstruct U.N. weapons inspectors. The second housed a Republican Guard headquarters and barracks.

"These units guard and transport Iraq's weapons of mass destruction," Shelton said. "They're part of the apparatus Saddam uses to maintain control of his weapons of mass destruction facilities."

The night's air strikes reduced both facilities to rubble. Missiles heavily damage four of the five barracks. Shelton said it was unknown if the barracks were occupied at the time of the attack, which occurred between 1 and 4:30 a.m., Baghdad time. Shelton said all allied pilots and air crews returned safely from the first night's strikes. There was no opposition from Iraqi aircraft, he added.

Cohen and Shelton praised U.S. forces for their professionalism and thanked the British for their strong support. "British forces are not only staunch allies," Shelton said, "they are also superb warriors."

At the time of the briefing, Shelton said, strikes were again under way. The second day's operations involved land-based aircraft, British Tornado attack aircraft, as well as Navy and Marine strike sorties from the deck of the USS Enterprise, he said.

More U.S. forces are on the way to the region to provide added flexibility, he added. The USS Carl Vinson was to arrive in the Gulf later in the day, and some stateside ground and air forces would begin arriving this weekend, he said.

The Pentagon leaders would not say how long Desert Fox would last. They said only that air strikes would continue until the United States met its objectives. If at that point Hussein persists in defying international will, they said, the United States will be prepared to take further action.

"If Hussein does not yield," Cohen said, "the United States will continue to contain him."

To date, the secretary said, Hussein has been unable to seriously reconstitute his weapons of mass destruction program or rebuild his military. He has been unable to get rid of U.N. weapons inspectors or economic sanctions imposed against Iraq.

"We intend to keep the sanctions in place and we intend to keep our forces on the ready," Cohen said. "In the event he attempts to reconstitute again or threaten his neighbors, we will be prepared to take military action once again."