The Trump Administration's plans for Iran are not clear: It speaks of the necessity of change in Iran, but we see no plans to effect change. What are likely next steps?
I wish I could answer. Donald Trump ran for president saying that the JCPOA was "the worst deal" and that he would reverse it. After certifying Iranian compliance, he decertified it, a technical step whose significance depends on Congress. More broadly, Trump came to office with radical opinions but little knowledge, no principles, and a tiny network, so he inevitably has had to rely on the conventional views of experts. The tensions between intention and practice are apparent, unresolved, and unpredictable.
How does the U.S. administration plan to stop Tehran's adventurism – by fighting proxies like Hezbollah, al-Hashd al-Shabi, or the Houthis?
The U.S. government provides some help to the opponents of these groups, but not much and is not committed to their defeat. Trump's benign view of Russia's President Vladimir Putin interferes with plans to push back Putin's ally Tehran.
The defeat of Al-Qaeda brought ISIS; will the defeat of ISIS produce yet another Islamic terrorist organization?
I'm not convinced that Al-Qaeda or ISIS has been defeated; they have suffered losses, to be sure, but their ideas live on. More broadly, no individual (Khomeini, Bin Laden) or organization is critical to the Islamist movement, which is based on an idea, not personnel. So, yes, the decline of one group leads to the ascent of another – until the Islamist dream is broken.
The head of Lebanese Army put his troops in alert and the Lebanese press talks of a new Israeli attack. Do you expect a new Israeli-Hezbollah round of fighting?
It's a real possibility. Returning home from its success in Syria, Hezbollah is likely to want to take on its ultimate enemy, especially as its missile and rocket arsenal can do potentially great damage to Israel.
Can the Sochi and Riyadh summits give a new impulse to the next UN summit on Syria in Geneva?
As I understand Sochi, it was Putin's effort to derail Geneva. And don't forget the Astana talks, another Russian-led effort to by-pass international negotiations. Diplomacy has failed to do more than "de-conflict" certain regions of Syria; I doubt it can achieve much more than that now.
What next in the volatile Middle East, where we find a proxy war between Iran and Saudi Arabia, the crises in Qatar and Lebanon, and the Libyan, Syrian, and Yemeni civil wars?
After building for nearly a century, we are now fully in the Islamist moment. All the issues you mention result from the rise of competing Islamist movements – Sunni and Shi'i, Ikhwani and Salafi, monarchist and republican, violent and non-violent. They also have boast adversarial leaderships and alliances. It will take decades for these rivalries to settle. In the meanwhile, I expect the region to sustain its reputation as the world's most volatile.