I'm not serious, but I have to agree with The E that this war is not going to happen, at least in the near future. Let me remind you that the current technology for making this possible is well within possibility as of now.
The colonisation of Mars, as well as the colonisation of space, is seen by Musk and others as a moral duty to ensure humanity's survival the same way a USB drive, Memory Crystal Storage drive, and 5D storage drives are meant to preserve data in an event of a computer crash. A Martian colony or a space colony could guarantee mankind survives in case of a debacle that destroys life on Earth. So, let me guess, to paraphrase Elon Musk: "You back up your hard drive. Maybe we should back up life, too?" Perhaps we should back up progress too.
I know global catastrophes take on many forms. We have a very long history of making steady progress. Nevertheless, this progress may be halted in the near future, and chances are high that humanity could regress back to the dark ages as a corollary of extremism, especially with the recent rises of Trump, Brexit, ISIS, white supremacists and neo-Nazis.
And the history of Star Trek where World War 3 does occur, but in the end, humanity ends up surviving. Hope humanity survives, not under some criminal neo-totalitarian fascist government like Putin's Russia.