ON October 29, 1969, Leonard Kleinrock, a computer scientist at the University of California, Los Angeles, tried to send the message “LOGIN” to a computer 350 miles (560 km) away at Stanford Research Institute (研究院) in Menlo Park, California. The big computers broke down, but “LO” was received. It was the first message sent using ARPANET (Advanced Research Projects Agency Network), the Internet's predecessor (前任). The ARPANET was built for the US Defense Department during the Cold War .