As a theory it would be falsifiable, no? So you should (a) be able to disprove it, and (b) provide evidence supporting your theory.
It cannot be proven nor disproven due to lack of evidence. Maybe in the future we will have that evidence but right now neither did you nor me provide any. However, it can be reasoned effectively that it is indeed plausible for the Internet to have been created with military ambitions in mind.
I'm still assuming your answer is "no", do please shout if you've come up with some new challenge to rational thought.
Your understanding of rational thought is funny to me. You could as well as present the diary of admiral Richard E. Byrd as evidence that the Earth is hollow.
Please, come back when you have evidence to support your claim that the Internet was not designed to withstand war. Until that, the common sense will answer the question for us all --- in network centric warfare the Internet is an inevitable invention and thus was probably created for that purpose. Was fire discovered or invented? What you're saying is like "the Internet was discovered". Being an axiomatic element to the network centric warfare, it is impossible for it to be an accident. Let me guess, you think life on Earth is also an accident? Evolution is the result of mere chance?