Reports are now quite clear that Mohsen Fakhrizadeh--the former head of Iran's pre-2004 nuclear weapons program--was the target of an assassination attempt in Iran. Who did it? Why? What are the likely consequences? How will Iran respond? A few thoughts...

1. Unsurprisingly, Israel tops the list of suspects. Why do it now? Because they know Trump may be more tolerant of this move than a Biden admin. And if it leads to an Iranian response that makes it harder for the U.S. to return to the JCPOA, that's a good outcome too.

2. That explains timing/tactics, but not the larger question of why do it at all. What's the desired impact on Iran? First, it sends a message to Iran--and to Iranian scientists--that they are being watched, and that they aren't safe.

3. It also no doubt undermines morale (they took out the big guy), and might temporarily disrupt whatever projects Fakhrizadeh might have been engaged in at SPND. It also probably eliminated a key source of institutional memory (and possible nuclear weapons advocacy).

4. But remember--and this is the important part--as of 2019 the US believed Iran had not restarted its former weapons program. So the impact of the assassination is likely more symbolic, and aimed at deterring/disrupting any future effort rather than stopping current activity.

5. (Of course, there's the chance that in recent weeks or months Iran did make a move to get its weapons program back online--in which case, that would be the bigger story. But so far, there's no public evidence of that.)

6. Whether or not the assassination will succeed in its likely goals is almost impossible to predict without more information. There's a good chance it both hardens resolve, but deters re-start. But the jury is still out on that one.

7. Will Iran retaliate? If so, how and when? This question is more interesting given that the anniversary of Soleimani's death is just over a month away. On the one hand, you could argue Iran may be motivated to act soon--prior to a Biden inauguration.

8. My guess: We won't see any major kinetic action from Iran between now and inauguration day. Or at least if we do it will be layered in plausible deniability, and largely fit the pattern we've seen to date (rocket attacks by proxies, cyber attacks, etc.).

Bottom line: These next few months are going to be rocky and unpredictable. This is also a reminder that we're still grappling with events that ended over 15 years ago. The ghosts of Iran's nuclear past are very relevant to our present.