Within hours of the Iraqi invasion of Kuwait, FBI headquarters in Washington sent bulletins to agents across the country asking them to step up monitoring of Iraqi nationals and groups that might pose terrorist threats, according to law enforcement sources.
At the same time, defense and intelligence officials began to review dozens of scenarios, examining potential threats to U.S. interests worldwide.
And in federal office buildings in Washington, teams of economists began calculations to determine how much of a threat a long-term confrontation with Iraq might pose to the international economy.
Like a stone thrown into a lake, President Bush's decision to commit U.S. power to stop Iraq's Saddam Hussein has sent ripples around the globe, concentric circles of danger to Americans detained in Iraq and Kuwait, to American forces in Saudi Arabia, to U.S. interests in the Persian Gulf, to the country's interests in the Middle East in general, to even broader national interests in Europe and Asia and to the world economy.
Just as the United States has tried to organize a worldwide embargo designed to choke Iraq's economy, Hussein has made clear that he regards U.S. targets anywhere as fair game.
"Burn the soil under the feet of the aggressors and invaders who want harm for your families in Iraq," an Iraqi government spokesman declared Friday. "Hit their interests, wherever they are."
And as the confrontation continues to escalate, with Sunday's announcement that the U.S. Navy will begin implementing a blockade of Iraqi and Kuwaiti ports, Bush Administration officials have begun sending warnings to the American public: The United States expects to win this fight but the victory will not come without cost.
Over the long term, the costs could include a severe worldwide recession, if the conflict badly disrupts oil supplies, or a loss of U.S. leadership if the international effort that Bush has cobbled together eventually fails to dislodge Iraq from its Kuwaiti conquest.
The current crisis is "the first test of a global crisis management system" that could be of enormous benefit in deterring future aggressors, said Augustus Richard Norton, a Middle East expert at the International Peace Academy in New York. But if the effort falls apart, "the world will be more unsafe as a result."
In more immediate terms, the threat that has attracted the most public concern is the risk to U.S. soldiers being sent to Saudi Arabia and the roughly 3,500 American citizens still in Iraq and Kuwait.
The last time American ground troops were sent to the Middle East, the deployment triggered a tragic terrorist act. The October, 1983, truck-bomb attack on the Marine barracks in Beirut killed 241 servicemen and eventually forced the United States to give up its attempt to end Lebanon's civil war.
The memory of that debacle still haunts U.S. policy-makers as they supervise the current force build-up in the Persian Gulf. Similarly, the President and his advisers are mindful of the long captivity of the U.S. hostages in Iran in 1979 and the continued imprisonment of hostages in Beirut.
Despite the public concern about those two threats, however, U.S. officials and private experts say they believe that the American troops and the U.S. citizens detained in Iraq and Kuwait--officials have studiously avoided calling them "hostages"--probably are safe for now.
In Beirut, the Marines were encamped in the midst of a city with a minimal defense perimeter, surrounded by a potentially hostile population. In Saudi Arabia, by contrast, U.S. forces are dug into desert positions that are isolated from population centers and difficult to approach.
Iraq could try to attack U.S. ships in the Persian Gulf, using its Silkworm anti-ship missiles, or it could launch an air attack to test U.S. defenses. But officials say they see no signs for now that Hussein is considering an all-out ground attack on the U.S. force.
As for the Americans in Kuwait and Iraq, they are "an insurance policy for Hussein," said one Pentagon analyst. Officials believe that Hussein is unlikely to harm his captives but that he will try to keep them as a shield against American attack.
Iraq has made ambiguous declarations about allowing foreigners to leave the country but, so far, only a handful have been allowed to go. At least one foreigner, a Briton, was shot and killed Saturday as he tried to leave Kuwait for Saudi Arabia, British officials said. About 4,600 British subjects are in Iraq and Kuwait, officials estimate.
Far more worrisome, officials say, is the possibility of an Iraqi-inspired attack on U.S. interests outside the immediate range of the fighting.
"There are several terrorist organizations that have found haven in Iraq and I have every . . . expectation that they're going to be asked to do something. We're paying attention," the commander of U.S. forces in the Middle East, Gen. H. Norman Schwarzkopf, said Sunday.
U.S. counterterrorism experts note that two of the Arab world's most notorious terrorists, Abu Nidal and Abul Abbas, both now appear to be running their operations out of Baghdad.
While the United States gets help from Arab leaders, the Iraqi president has sought to build support among the masses, positioning himself as a defender of Arab nationalism and denouncing his opponents as part of a conspiracy linking the United States, Israel and wealthy "emirs of oil."
"This incitement to groups outside of Iraq to rise up and strike" could easily lead to terrorist attacks, a Pentagon analyst said.
Attacks in the United States are a possibility, although law enforcement officials say that no credible threats have yet been seen.