Yet the Trade Center case and its sequel, the indictment of Sheik Omar Abdel-Rahman and 14 other suspects in an alleged plot to bomb United Nations headquarters and other New York City locations, pose a dead serious risk to the United States. If the government is right, a motley assortment of amateur terrorists successfully concocted powerful explosives from chemicals – fertilizer and fuel oil – that are widely available to anyone. Six people died in the Trade Center blast and 1,000 others were injured. In the second plot, prosecutors say, the conspirators planned to detonate four bombs more or less simultaneously at U.N. headquarters, at FBI headquarters in lower Manhattan and in the Lincoln and Holland tunnels. Such an event would have created an unprecedented public emergency in New York – and the target could just as easily have been any city in America.

Ignore, for the moment, the questions of who is guilty, who is innocent and whether the government can win either case: the jury begins its deliberations in the WTC bombing this week, and the second trial is scheduled for September. What is arguably the most disturbing aspect of these parallel investigations is the fact that nobody has been able to produce a convincing explanation of why any of it happened. There is no unifying thread – no motive, as American juries usually understand it. No one has stated a coherent reason for bombing the World Trade Center, and no one has yet been able to provide a motive for the second plot, either. The best we have are vague references to U.S. support for Israel and Egyptian President Hosni Mubarak, plus a cryptic threat allegedly issued by one defendant, Siddig Ibrahim Siddig Ali, that the plot to bomb the World Trade Center would show America that “we can get you any time we want.” For what, exactly? And why now?

You can argue, as some do, that the 22 defendants named in these indictments were motivated by the tradition of Islamic militance and the bitterness of 20th-century Arab history – that they shared a common belief in the cleansing power of jihad, or holy war, and a common hatred of the Great Satan. Sheik Omar, an Egyptian fundamentalist and a fiery preacher, was jailed and tortured by Egyptian police after the murder of President Anwar Sadat, and he is Mubarak’s foremost opponent today. His sermons, delivered in a shabby mosque in Jersey City, N.J., and relayed throughout the Arab world, were full of diatribes against the Egyptian government an Western secularism. But in a recent interview with NEWSWEEK, the sheik, now being held in a federal maximum-security prison in Manhattan, disclaimed hatred for the United States, “a country I chose to come to, whose people are very generous.” He said he had been encouraged by Bill Clinton’s election because it would “remove the shadow of war in the Middle East.”

Even assuming Rahman is concealing his true beliefs, it is hard to see the other 21 defendants as a close-knit terrorist cell. They are a disparate group – Palestinians, Jordanians, Sudanese, Iraqis and even two Americans, Victor Alvarez, a Puerto Rican convert to Islam, and Rodney Hampton-El, a black Muslim from Brooklyn. What united them, some say, was their fervent support for the Afghan mujahedin in their nine-year rebellion against the Soviet occupation – a successful, real-world jihad. Hampton-El actually served in Afghanistan as a medic. Two other defendants, Mahmud Abouhalima and Ibrahim Elgabrowny, apparently served in Afghanistan, too. Three others, including Sheik Omar, visited Afghanistan and neighboring Pakistan to show their support for the mujahedin. Some may have received paramilitary training, including instruction in how to make explosives, while they were there. Prosecutors in the WTC case, for example, argue that the Trade Center conspiracy actually began in Peshawar, a Pakistani border town that served as an operations base for the Afghan freedom fighters.

The Afghan war, in short, became an incubator for militant jihads in other countries. But this theory does not explain why Muslim extremists would attack the United States, which covertly supported the mujahedin for years. It also does not explain the timing of the World Trade Center bombing.

But the gulf war might. As investigators have noted from the beginning, the Trade Center explosion occurred on Feb. 26, 1993, the second anniversary of the day that allied forces encircled and destroyed the Iraqi Army in Kuwait. Egyptian intelligence officials, who captured and interrogated Mahmud Abouhalima, have been pushing this notion for months.

U.S. investigators say the man who apparently directed the Trade Center bombing, Ramzi Ahmed Yousef, was an Iraqi citizen who entered this country in the fall of 1992 and made contact with some of Sheik Omar’s admirers in Jersey City. According to the FBI, Yousef shared an apartment with WTC defendant Mohammed Salameh and bought the chemicals that were used to make the Trade Center bomb. Investigators say Yousef left the United States the day the bomb went off and was last seen in Afghanistan. Washington is offering a $2 million reward for Yousef and $2 million more for an alleged accomplice, Abdul Rahman Yasin, who is known to have fled to Iraq. Last week Salameh’s lawyer called Yousef “an evil genius” and said he duped and manipulated his client.

The timing, together with the involvement of two shadowy Iraqis, of course suggests that the Trade Center blast could have been Saddam Hussein’s revenge. U.S. officials emphatically deny that theory, saying there is no evidence Baghdad played any part in the World Trade Center conspiracy. The circumstantial evidence is tantalizing – but unless one of the suspects confesses, we may never know for sure.