As late as the Napoleonic era, wars were conducted in a different method than they are today. For example, when two armies met on the battlefield, after coming face to face, just before they began the conflict the commanders on each side would meet and possibly agree a start time to the battle, say 9:00 a.m the next day. It is not too difficult to see the advantage one army would have over the other if it mobilized its forces an hour earlier, say at 8:00 a.m.
But certain events and weaponry and techniques are game changers. The day that nuclear weapons were invented, the game changed. The day that chemical weapons made an appearance, the game changed again as it did with the invention of biochemical weaponry. Not having the money or technology to develop weapons was irrelevant, since in many cases it could be stolen as indeed could the inventors of such weaponry. In short, day by day, conflicts are getting more and more dangerous.
We always had one thing in favour of mankind. Once a deal was struck (treaty), it would very much stay in place until the terms and conditions were broken by one or the other side. Now we have a new game. Tearing up the treaty just for the hell of it. In truth it's not new. When a dictator makes a deal, the good guys on the other side are never satisfied. They will lie, invent and push the bad guy until war is inevitable. When the bad guys falls, a vacuum is created and the resentment, conflicts and opposing forces that fill this vacuum are, more often than not, uncontrollable. Perhaps? Let us not forget that they were being controlled, by the dictator, before he was removed from office.
Regime change, especially in a divided area where the religious divide is as wide as the national one, destabilization is very dangerous indeed. All efforts to bring this about by peace by warring methods (from the west) have failed. From Iraq, Libya, even Egypt and now Syria, the result was the same. A mess. By the way, let's not forget the days of US meddling in Central and South American regimes.
Let us assume for a second that Trump's new policy forces Iran back to the negotiating table. Already it has cost Trump respect and control at the helm of the NATO ship. Europe now is as likely to push for its own independent army as it is to
increase its contribution to NATO.
On the other hand, the Arab Sunni - Shia divide is as wide and as vicious today as it has ever been. If the Western nations, would spend more time trying to resolve this problem, rather than arming their ally of choice, perhaps we might get some real peace. There is a delicate balance in Iran at the moment. The Iranian President Hassan Rouhani a sort of moderate, vs. Supreme Leader Ali Khamenei. Tearing up this agreement has weakened the moderate.
The West, lead by the US has time and again proven that they cannot grasp the concept of the balance in the Eastern regimes and messing with them simply disturbs whatever equilibrium there is at the moment. Where the new equilibrium point will be is still unknown. Mess with this at your own risk.