President Bush has dispatched a shadow government of about 100 senior civilian managers to live and work secretly outside Washington, activating for the first time long-standing plans to ensure survival of federal rule after catastrophic attack on the nation's capital.

Execution of the classified "Continuity of Operations Plan" resulted not from the Cold War threat of intercontinental missiles, the scenario rehearsed for decades, but from heightened fears that the al Qaeda terrorist network might somehow obtain a portable nuclear weapon, according to three officials with firsthand knowledge. U.S. intelligence has no specific knowledge of such a weapon, they said, but the risk is thought great enough to justify the shadow government's disruption and expense.