What was one of the fundamental requirements for the new national computer network proposed by the DoD in the 1960s?

One fundamental requirement for the new national computer was that the network should be sufficiently robust ie, strong enough so that even if some network nodes were lost to sabotage, war or some other cause, the network would continue to function. This was chosen as the fundamental characteristic because the robustness was the major issue back then and it was hence important to make the network physically secure rather than any other security. Since this was proposed in 1969 back then there was a period of war and the network used to get destroyed due to various physical factors such as natural calamity, war, etc. Hence we consider it the primary requirement.