Trump is tweeting threats to Iran. Will he invade Iran? I'm going to bet on no. The odds are far higher than I would like for a country that isn't invading anyone else and that didn't violate the nuclear deal, but I'm going to bet on no. For now. Trump is easily distracted, and he's just venting, because he had a bad week. However, that may give you an indication of where this is going. Keep an eye on these things.
1. Watch the 2018 midterms. With a Democratic congressional majority, he'd have zero chance of any legislation, and if Democrats take the Senate, he won't even be able to appoint anyone to anything unless he actually consults with Democrats, and... that ain't gonna happen. The more frustrated Trump gets on the domestic front, the more his attention will turn to international aggression as an outlet.
2. Watch Mueller. This is part Wag the Dog, and part frustration, but if Mueller really does get too close to Trump personally, launching a war would seem like a good distraction to him. How close is Mueller to Trump personally? We don't know. Mueller runs a tight ship. Things are looking ugly between Trump and Cohen, though, and if Cohen flips, that's bad for Donny-boy. The more frustrated and scared Trump gets, the more he'll want to take that out on someone, and try to distract the country.
3. Watch the trade war. In case you missed this, Trump indicated at the end of last week that he is willing to slap tariffs on everything China sells to the US. Full trade war. Because Trump is a mercantilist idiot. Sorry for the repetition there. The more fallout there is from Trump's trade war, the more Trump may get frustrated, and want a distraction.
4. Watch the rest of the world. Trump is getting skewered by everyone around the world. Nobody takes him seriously because... seriously! He practically blows up NATO, slobbers in Putin's lap, sucks up to Kim Jong Un, starts a trade war with our allies for nothing... If he gets the sense that the only way to make world leaders see him as the tough guy he wants to be is to find someone in the prison yard and beat him up, he'll do that, because right now, world leaders don't see him as a tough guy. They see him as Putin's lap dog. Invading Iran wouldn't eliminate the Putin part, but at least it would puff up his chest. Remember, Trump isn't smart.
5. Watch Iran. Notice I put this last because this really doesn't have anything to do with them. If Trump's Iran tweets seemed to come out of nowhere, that's because they did. This isn't about Iran. This is about Trump puffing up his chest. North Korea? Now that Kim Jong Un is Trump's second-bestest buddy (after Putin, of course), he isn't likely to posture about war with them, so Iran was the likeliest target. However, Iran's responses could influence how this plays out. A few days ago, I posted this about Trump's need for dominance games, and how that conflicted with his behavior with Putin. Trump is now back to calling Russian meddling a "hoax," after having his advisors and the press twist his arm into briefly admitting the truth. Now, he needs to puff up his chest again and play his stupid, little dominance games. He actually can invade Iran. They don't have nukes, so he doesn't have to worry about that. He doesn't need congressional approval. War Powers Resolution. Iran has a fine line to walk, then, of not just kowtowing to King Joffrey, but not giving him enough provocation for an actual war. So, yes, watch Iran. Fortunately, Iranian leaders are smarter than Trump. Everyone is smarter than Trump.
Most of this boils down to the issue of Trump's frustration. For all of his tough guy posturing, what he wants is for everyone to fall to his feet and praise his toughness so that he doesn't have to do anything. Wars are work, and they are risky. The likelihood that he will actually attack Iran is low, and the likelihood that they will attack us is zero. However, the more Trump's frustration builds about other matters, the more he will look to military conquest as an outlet, hoping for what we call a "rally 'round the flag" effect, in which presidential approval numbers go up in times of national crisis. Would it happen for Trump? I'm skeptical. As Richard Brody has argued, the effect happens when there is "elite consensus," and I doubt that Democratic elites would give Trump cover for an unprovoked invasion of Iran, just to cover his own political ass, in which case the move wouldn't work. That doesn't mean he wouldn't try it, though.