I think that with our Current Destructive Technology, how we fight World Wars now will be very different to how the First and Second World Wars were performed. WW3 is more likely to start with a Nuke Detonating in American Territory. America then retaliating and firing on a suspect country and it all progressing from their.....
Think about this.. The WTC act, tock over seven years of planning to execute... The next major act could take another seven years, (they have all the time in the world to prepare and we have all the time in the world to wait) And I don't think it will be from firing a Nuclear Tipped Missile towards America from a Rouge State.. It is more likely to be slowly constructed in a brought Building maybe even Hired Penthouse Suit, in one of America’s major states (Washington would suffice for a political statement).. No missile defense shield will stop it.. Because it will detonate right under everyone’s nose..
Even if it means Twenty Extremists a year, smuggling a Uranium Capsule up their ass through the airports or via Merchant Ships.. And then handing it over to the other waiting groups members, once on America soil.. This could very well become a reality..
This is what could start it... you don’t need a Missile to Detonate a Nuke.