Just like holding anything in Afghanistan is impossible for tactical reasons, and invading Russia is impossible for logistical reasons (unless you come from Mongolia, of course), maintaining a war against Iran has been impossible for economical reasons since the Middle Age.
And apparently adding Eastern Africa to any imperium will destroy it too, but I can't imagine why that is.
After China, South Korea, and Japan getting together, I'm not even sure this one is his greatest peacemaking action.
But then, Iran used to be the one place in the Middle East where those two lived in peace.