Defense Advanced Research Project Agency (DARPA) was established by the U.S. Department of Defense (DoD) to research and implement scientific-military discoveries.
One of the projects of DARPA, which grew out of ARPA and was renamed in the 1960s, was to build a packet-switched communications network that would remain fully functional even if vital links were destroyed, such as in a nuclear first strike.
This project was the Advanced Research Projects Agency Network (ARPANET), which later became the Internet. In the 1970s, the Transport Protocol (TP) and the Internet Cache Protocol (ICP) were implemented for packet-switched operation of various transmission mechanisms. In the 1980s, the military part, the MILNET, was separated from the ARPANET.