Last month's terrorist bombing at the U.S. Military Training Mission in Saudi Arabia, like the proverbial tree in the forest, went largely unheard. Yet it portends a mounting threat to the kingdom's stability coming not from outside enemies or even traditional dissidents but from some of the most privileged sectors of Saudi society. PNS analyst Peter Theroux is a writer and author of "Sandstorms" (W.W. Norton) and a translator of Arabic literature.

One month ago, on November 13, a booby-trapped van exploded in the parking lot of the U.S. Military Training Mission in the Saudi Arabian capital, Riyadh. Five Americans were killed in the bombing, which instantly dropped out of the news. This is not surprising; no foreign news agencies are allowed to maintain bureaus in Saudi Arabia, whose government has a plutocrat's mania for privacy. Saudi citizens were, for example, the last people in the world to learn that King Fahd had a stroke last week, and that the 73-year-old monarch's condition had stabilized.

The stability of the country is something else. Commentators have made much of the king's age, diabetes, chain-smoking and generally dissolute life, but little such scrutiny has been trained on the regime itself, which governs as an absolute theocratic monarchy with no constitution.

While Saudi Arabia is an educated, prosperous and even luxurious country, there are no elections, political parties, or labor unions; no freedom of religion, no freedom of assembly, speech or of the press; incoming newspapers and magazines are heavily censored. Women are not allowed to drive; no Saudi has ever cast a ballot. Without petroleum wealth, the political landscape of Saudi Arabia would resemble that of the most repressive regimes of the Marxist era -- Albania or Ethiopia.

Instead of encouraging reform in Saudi Arabia, the U.S. government has traditionally indulged this pliable ally. Saudi Arabia, after all, is an immense market for American goods, especially military hardware; has always had a horror of Communism; and has cooperated in a wide range of American adventures like arming the Nicaraguan Contras. Nor is it a bloodily repressive regime: it has historically bought off its enemies, domestic (there was a recent amnesty for vocal Shi'ite dissidents) and foreign (the PLO, Yemen, Iraq before 1990). As the holy land of Islam, the kingdom's views have been thought to carry weight with the world's nearly one billion Muslims.

And with a national population the size of a large U.S. city in charge of a quarter of the world's oil reserves, the kingdom is unquestionably vulnerable and in need of foreign patronage. The received wisdom has always been that Saudi Arabia must scan the horizon for deadly threats abroad: Marxists, Arab nationalists, Shi'ites, secularists, and crude looters like Baathist Iraq.

The explosion in Riyadh was a straw in the wind. The problems that eventually demolish the absolute theocratic monarchy in Saudi Arabia will come not from the regime's enemies but its friends: a too visible American Big Brother, and the extreme Sunni Islamic movements Saudi Arabia has always funded and promoted, which are now turning against their benefactor -- in Lebanon, in Sudan, in Egypt, and wherever the Muslim Brotherhood exists.

Although the regime has made conciliatory gestures toward its Shi'ite citizens (knowing that Iran is watching) it is the Sunnis that now cost Fahd sleep. The generation of young technocrats that grew up rich and was educated in the United States, once thought to be on the brink of running the country, have stayed on the brink while corrupt royals have continued to rule -- and loot -- the country.

One of these is Prof. Muhammad Abdallah Misari, whose Friday sermons at the University of Riyadh Mosque in the mid-eighties infuriated the government by attacking Saddam Hussein. This was during the Iran-Iraq war, when the Saudi regime supported Iraq. "We will have change in this country," the ever-cheerful, Berkeley-educated Misari observed at the time. "I just hope it won't be bloody."

During Desert Storm, Misari again ruffled royal feathers by opposing the alliance of sheikhdoms and great powers, and was quickly fired, arrested and exiled, along with his equally outspoken father. They head up the nonviolent Committee for Legitimate Rights in London, which has denied any involvement in the Riyadh bombing. And yet the Misaris are Riyadh's worst nightmare because they are what the royals falsely claim to be -- devoutly and uncompromisingly Islamic, anti-corruption, and opposed to foreign entanglements.

Those are the regime's peaceful enemies. The violent ones, known in Arabic as "Arab Afghans," are the Muslims -- Saudi sons of privilege, unemployed Egyptians, Algerian holy warriors -- who fought beside the Afghanis to force a Russian pullout. Whether or not the Arab Afghans bombed USMTM is not certain; but the bombers certainly are in sympathy with them.

Ironically, the Saudis heavily bankrolled the fanatical Afghan movement, working closely with Washington. The enemy was Russia's puppet regime in Kabul -- Muslim stooges who were more interested in self-preservation and pleasing their superpower patron than in any principle of Islam, democracy, freedom, or even good sense.

The stooges lost. The Saudis should be reminded that they always do.