It was George W. Bush who reacted to the 9/11 attacks as a manifestation of Evil, imposing upon the United States the duty to extirpate the Foul Fiend and his offspring Terror, so as to restore Virtue by means of global war.

This was completely familiar moral territory to 21st century Americans, who had never in 150 years fought a war that was not described in the language of religion. From 1861 forward, Americans were trampling out the vintage of the Lord’s wrath, answering the call of His trumpet that would never sound retreat, calling Americans to die to make men free. A noble task, if by now become a hollow one.

George Bush’s overwrought and misdirected war against global terror, conceived as a war of the Righteous to destroy Evil, having failed wherever it was launched, has now been reconceived under Barack Obama as a war against what must be called the disparate disorders and political dysfunctions of an Islamic society still in search of a constructive non-theocratic place in 21st century history. Whether Obama, like his predecessor, also sees what now is his war in apocalyptic terms, we do not know.

However, if Osama bin Laden’s own statement of responsibility for 9/11 is believed, the attacks on New York and Washington had a specifically religious motivation in America’s unwanted military presence in Saudi Arabia in proximity to Islam’s Holy Places. The “war on terror” exhibited its provocative religious character for Muslims in the deployment of American military forces in the Middle East — specifically in Saudi Arabia, with its Holy Places, under the Reagan administration in 1983, which created a general Middle Eastern regional American military deployment known as Central Command.

According to Dana Priest’s indispensible history of these military developments (“The Mission,” 2003), CENTCOM Gen. Anthony Zinni ended his term of command in 2000 in considerable sympathy with Arab regime resentment or open hostility to American deployment pressures and base locations. The movement bin Laden subsequently created was religious in nature, descended from the Muslim Brotherhood that originated in Egypt, and obviously under the influence of the profoundly conservative Wahhabi religion of bin Laden’s native Saudi Arabia.

All but four of the 19 people taking part in the 9/11 attacks were Saudi Arabians. The modern Islamic jihadist movement is motivated by religion, the dominant strain found among Shiite Muslims, whose base has been in Iran since the revolution in that country in 1979, and the Sunnis under the influence of the Wahhabi tradition and the Muslim Brothers of Egypt. Its current effort has been to establish theocracies in emulation of the medieval Islamic system. They must see that it is already failing to do so in the places where it is being attempted: Tunisia, Egypt, Syria, the once and future Afghanistan and the Muslim Caucasus.

However, the deepest motivation for Islamic zealotry and its acts of terrorism is something else, which ought to be very familiar to Americans. Its fundamental if unrecognized impulse has been nationalism. Nationalism drove the post-revolutionary wars of continental Europe, revolution in France having inspired the modern nation-state and its own crusade against dynastic states, ruled by and representing family dynasties, a system forged in medieval Europe and destroyed by the revolt of the peoples in France and the Napoleonic Wars’ assault upon the existing system.

Out of that century came the Europe (and North America) of nations and national power. The First World War confirmed it (while also confirming the dominance in the Arab world of European colonialism). The Second World War produced the effort to end nationalism in Europe, while producing the American nationalist superstate, whose ultimate fortunes we have yet to see.

This confusion of nationalist motives with religious ones in the Middle East has produced profound misunderstandings in Washington that persist to the present day. Despite President Bush’s garbled talk in 2001 about crusades, and the hysterical beliefs subsequently expressed in teapot Republican circles about the threat of Shariah law in America and of a new Muslim global caliphate conquest of the West, Arab terrorism has in official policy-making been treated as political in origin and a matter of specific groups and leaders, only indirectly linked to foreign governments (Iran excepted).

President Obama today fires his drones’ rockets against supposed al-Qaida leaders and terrorist activists and bands across the length of the Mediterranean, who are infiltrating Africa and finding sympathizers among restless and jobless youths in immigrant neighborhoods in Western Europe. These recruits often are latecomers or even converts to Islam and jihad as forms of defiance directed against their circumstances in Europe, or adhere to glamorous foreign causes about which they actually know little.

The Pentagon and Obama’s White House seem to have concluded that as America has failed to impose its power and control over the Arab world by means of major military interventions and “surges” of modern military technological superiority, it now can do it by killing all the jihadists (and their followers and families), one by one, with drones. One does not have to be a prophet to say that this also will fail.

Visit William Pfaff’s website for more on his latest book, “The Irony of Manifest Destiny: The Tragedy of America’s Foreign Policy” (Walker & Co., $25), at www.williampfaff.com.