GREAT POWERS cease to be great for many reasons. In addition to the causes frequently debated -- economics, culture, disease, geography -- there is an overarching trend. Over the last 500 years, the fate of nations has been increasingly tied to their success, or lack thereof, in harnessing revolutions in military affairs.

These are periods of momentous change when new technologies combine with new doctrines and new forms of organization to transform not only the face of battle but also the nature of the state and of the international system. Because we are in the middle of the fourth major revolution since 1500 -- the Information Revolution -- it is important to grasp the nature and consequences of these upheavals.

Until the 15th century, the mightiest military forces belonged to the Mongols. But strong as they were in the days of bows and arrows, the Mongols could not keep pace with the spread of gunpowder weapons and the rise of centralized governments that used them. They fell behind, and Europe surged to the forefront. In 1450, Europeans controlled just 15% of the world’s surface. By 1914 -- following not only the Gunpowder Revolution but also the first Industrial Revolution -- their domain had swollen to an astounding 84% of the globe.

Not all European states were equal, of course. Some early leaders in gunpowder technology -- for instance, Spain and Portugal -- were also-rans when industrialization began in the 18th century. At least Spain and Portugal managed to maintain their independence. Numerous others -- from Poland to the Italian city-states -- were not so lucky. They endured prolonged occupation by foreigners more skilled than they were at new forms of warfare.


The big winners of the Gunpowder Revolution (from roughly 1500 to 1700) were the northern European states, from Britain to Russia. But the Romanovs, Habsburgs and Ottomans did not survive the cataclysmic conflict of the first Industrial Age -- World War I -- and their empires collapsed, even as Germany and Japan were catapulting themselves into the upper rank of nation-states largely through their growing military expertise. World War II -- the major conflict of the second Industrial Revolution, defined by the internal combustion engine, airplane and radio -- further shook up the international balance of power.

The conventional assumption is that the outcome of World War II was virtually foreordained: The Allies won because they were bigger and richer than the Axis. There is some truth to this. But by 1942, Germany, Italy and Japan controlled most of the natural resources of East Asia and Europe. This would have allowed them to match the Allies if they had been more adept at marshaling their military and economic power. The Soviet Union and the United States -- the biggest beneficiaries of the second Industrial Revolution -- did a better job not just in managing wartime production. They also grabbed the lead in the use of such key weapons as the tank (the Soviet Union) and the long-range bomber and aircraft carrier (the U.S.). There are many reasons why once-dominant powers such as France and Britain had become second-tier ones by 1945, but central among them was their failure to exploit advances in weaponry during the inter-war years.

The Information Revolution of the late 20th century upset the seemingly stable postwar order. The Soviet Union had no Silicon Valley and could not compete with the United States in incorporating the computer into its economic or military spheres. U.S. prowess at waging war in the Information Age was showcased in the 1991 Persian Gulf War, which, along with the collapse of the Soviet empire, left the United States standing alone as a global hegemon.

But if history teaches any lesson, it is that no military lead is ever safe. Challengers will always find a way to copy or buy the best weapons systems or develop tactics that will offset their effect. Our most formidable enemies, Al Qaeda and its ilk, have done both. They are using relatively simple information technology -- the Internet, satellite television, cellphones -- to organize a global insurgency. By using such weapons as hijacked airliners and bombs detonated by garage-door openers, they are finding cracks in our defenses.


We have an insurmountable advantage in high-end military hardware. No other state is building nuclear-powered aircraft carriers, stealth fighters or unmanned aerial vehicles. In fact, we spend more on the development and testing of new weapons -- $71 billion this year -- than any other country spends on its entire defense. But all that spending produces weapons systems that aren’t much good for pacifying Baghdad or Kandahar.

Technology isn’t irrelevant to the global war on terror. We can use powerful surveillance systems to break up terrorist plots. And “smart bombs” can be invaluable for dealing with the perpetrators. But our enemies can stymie multibillion-dollar spy platforms by using couriers instead of satellite phones, which helps explain why Osama bin Laden remains on the loose.

New revolutions in military affairs, possibly centered on biotechnology and cyber-war, promise to give smaller states or sub-state actors more destructive capacity. Imagine the havoc that could be caused by a genetically engineered contagion combining the worst properties of, say, smallpox and the Ebola virus. Or imagine how much damage our enemies could inflict by using computer viruses -- or directed-energy weapons -- to immobilize critical bits of our civilian or military computer networks. In theory, it’s possible to crash stock markets, send airliners plowing into the ground and blind our most advanced weapons systems.

The most threatening weapon of all harks back to an earlier military revolution. Nuclear bombs haven’t been used since 1945, but given their proliferation around the world, it will only be a matter of time. Our scientific sophistication gives us a reasonable chance of shooting down a nuclear-tipped missile, but a nuclear suitcase smuggled into the U.S. would be much harder to detect.


To stop such stealthy threats, we need to get much better at human intelligence, counterinsurgency, information operations and related disciplines. We need more speakers of Arabic and Pashto, more experts who understand tribal relations in Iraq’s Anbar province and Pakistan’s Northwest Frontier province, more diplomats who can win over audiences on Al Jazeera. And we need to set them loose without having to worry about a burdensome bureaucracy micromanaging their every move.

It may sound melodramatic, but the future of U.S. power rests on our ability to remake a government still structured for Industrial Age warfare to do battle with decentralized adversaries in the Information Age. After all, aren’t we the mightiest, richest nation in history? How could our hegemony possibly be endangered? That’s what previous superpowers thought too. But their dominance lasted only until they missed a revolutionary turn in military technology and tactics.