LONDON — In a prominent hadith, the Prophet Muhammad said: "If disorder threatens, take refuge in Yemen." The prophet was referring to the prosperous and civilized Yemen. But today disorder and radicalization in Yemen are beginning to infect Saudi Arabia, and thus the safety of the world's largest oil producer.

The prophet's hadith about Yemen has enjoyed new resonance ever since the 1980s, when Saudi Arabia — in line with American policy — sought to export domestic dissenters, most prominently Osama bin Laden, a Yemeni of Saudi birth, to fight Soviet infidels in Afghanistan. Although dissent was mostly diverted to Afghanistan, bin Laden's most trusted companions (his wife, too) have remained mainly in Yemen.

In the wake of the Taliban's ouster in Afghanistan, bin Laden and his followers have come to regard Yemen, alongside Pakistan, as a haven. Indeed, Yemen is now a bubbling caldron of jihadis who have flocked there because it, like Afghanistan and Pakistan, has weak, easily manipulated state institutions. U.S. President Barack Obama's recent order to shut down the Guantanamo Bay detention facility has made the problem of Yemen's weakness a leading international issue. One-third of the Guantanamo detainees are Yemeni, but Yemen cannot guarantee the United States that the detainees will be controlled effectively if they are returned home. This fear is real. Many previously released Guantanamo inmates have disappeared underground.