THE INTERNET DID not spring up overnight. It has roots that go back almost as far as computing itself. The first computers were built in the 1940s, just after World War II. The early machines, such as ENIAC, were huge, expensive, and rather fragile because they used bulky vacuum tubes to perform calculations and store numbers. Because these computers were so large and expensive, only a few large corporations and government agencies used them.

By the 1950s, the Cold War between the United States and the Soviet Union was under way. Military planners had to deal with a world where nuclear-armed bombers and missiles might attack with little warning. They began to use computers such as a giant machine called SAGE to coordinate radar sightings and plan counterattacks.

In the 1950s, a "think tank" called the RAND Corporation concluded that...