These are all theories so they have no truth to them but at the same time it's all possible. I myself tend to remain a skeptic on "the end of the world" and other theories of Nostradamus but I still do not doubt them.
There is endless causes and effects in this world, take Bethesdas latest work "Skyrim" in it you find the elder scroll, the truth behind the elder scroll is that there is unlimited possibles all possible. For example 5 years from now we could all be dead due to a meteor or aliens (unlikely) at that same time there is a multiplicity of other possible things that could happen. (Fate is always changing even when decided)

Though world warIII it will happen no doubt, my own theory towards it is completely different to Nostradamus. It revolves around project bluebeam being legit, and with the evidence and suspicions behind it and also suicides and strange unexplainable heart attacks I've come to a self proclaimed conclusion this is real. How this will start the world war is well simply it affects the whole world, to have the world under one order similar to the illuminati would cause immense revolt, but if what I've read is true it will not simply be a war it will be a masacre of 1.5 - 3 billion. One relegion, one nation, one government. That will be the only empire that survives forever.
"Fair is Foul and Foul is Fair" - Macbeth.