I've been watching UFO and one episode, "The Dalotek Affair", opened with this interview of Doctor Frank Stranges by the future SHADO communications officer. Since curiosity is my fatal weakness, I looked up Frank Stranges and yes, he was a real person.

He was a lecturer on UFOs and claimed to have met an alien named Valiant Thor.

I didn't go much further down this particular rabbit hole but you choose to continue, make sure you have your tin foil hat and your Bible.

And as for that MacArthur quote, Snopes says it's false or at least misleading. MacArthur may have made reference to an eventual interplanetary war but not that it was any way imminent. But the quote does fit in perfectly with the premise of UFO.