James Acton
Co-director of the Nuclear Policy Program at the Carnegie Endowment For International Peace. I spend a lot of time thinking about nuclear weapons, advanced nonnuclear technology, and escalation.
- I'm thrilled to have a contract with @academic.oup.com for my book on "Entanglement and Unintended Escalation." (There'll be a better title!) The manuscript is drafted and currently being revised. Hopefully should be out second half of next year!
- Let's not nuke ourselves in the foot! I explain why it's so difficult to know if China and Russia are conducting ultra-low yield tests and why, even if they are, it's not in U.S. interests to restart testing. @carnegieendowment.org @carnegienpp.bsky.social carnegieendowment.org/emissary/202...
- I am entirely indifferent whether, in the event of a nuclear war, I am incinerated by a nuclear warhead delivered by a "traditional" ICBM, a hypersonic glider, a nuclear-powered cruise missile, or a nuclear-powered torpedo. All seem equally suboptimal to me.
- ¯\_(ツ)_/¯
- The End of MAD? Join me, Steve Fetter, @jaysankarans.bsky.social, TD MacDonald, Ton Stefanik, @lauraegrego.bsky.social, @fiona-cunningham.bsky.social, and Charlie Glaser to discuss whether technological developments are undermining mutually assured destruction. Link for virtual rego in next post.
- Here's the link for rego: airtable.com/appGGluMUVck...
- The conference is based on a series of papers we published in the Journal of Strategic Studies. Many are open access (no paywall!). airtable.com/appGGluMUVck...
- I feel pretty strongly the @nytimes.com has the wrong framing here. This isn't serious; it's pathetic. I'd suggest something like: "Trump throws social media hissy fit invoking nukes after public spat with ex-president of Russia."
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- Yes, absolutely.
- We now go live to the Kremlin for Putin's reaction:
- As much as I deplore nuclear signaling by tweet--can't believe I just wrote that--I would NOT necessarily assume there's a been change to the US nuclear posture. The U.S. always keeps ~4/5 SSBNs at sea ready to fire.
- From Nuclear Notebook in @BulletinAtomic tandfonline.com/doi/figure/1...
- Ooops. Wrong handle: @scientistsorg.bsky.social
- Ahem (Deleted earlier version, which was missing caption!)
- Ah, yes, that crucial ninth significant figure...
- Good gracious, Ignatius! Why I disagree with the normally excellent David Ignatius; recent oped on Iran.
- Ignatius's oped is written as if it's a news story. The "news" in this case is that--SURPRISE!--an Israeli source backed up claims by the Israeli government! (3/n) x.com/james_acton3...
- The case for attacking Iran relied on emphasizing its technical prowess. The case that strikes were successful requires claiming that Iran is technically incompetent. foreignpolicy.com/2025/07/25/i...
- On Friday, I argued in @foreignpolicy.com that Trump admin claims it had set Iran back by "years" were true but disingenuous. The same day, the normally excellent David Ignatius amplified the misleading U.S. and Israeli narrative. www.washingtonpost.com/opinions/202... Let's take a look... (1/n)
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View full threadGiven the U.S. developed the uranium metal production process in the 1940s in a university lab with equipment from the 1920s, why do you suppose Iran will struggle to replicate the process outside of Isfahan? (11/n)
- And, finally, given that hope is not a strategy, what's your plan to keep Iran in the NPT and to accept inspections--including of the 60% HEU that Israeli officials acknowledged survived the strikes. (12/12)
- What's Israel's plan for dealing with the HEU that Israeli officials acknowledge survived the attack? Does Israel know the location of Iran's stockpile of centrifuge components, which have not been under monitoring since 2021 following the Iran Deal's collapse? (9/n)
- The U.S. did not even try to collapse the very deep tunnels at Isfahan where most of Iran's HEU was stored. Are you concerned that, in reality, the United States has clearly signaled the limits of ability to destroy underground facilities with nonnuclear weapons? (10/n)
- Finally re timeframe, as Eric has observed, the claim that Iran is 1-2 years from the bomb is actually similar to pre-war estimates, including from NETANYAHU himself. (7/n)
- To close, some questions for Ignatius' source. What happens if "activities" are being conducted too far underground for Israel to destroy? Do you expect the U.S. to attack again? If yes, what happens if the activities are too deep for the U.S. to reach? (8/n)
- Moreover, both Netanyahu and Ignatius are being inconsistent in defining success. Netanyahu attacked the Iran Deal on the misleading grounds that its limits only lasted 10 years. Now Israel is claiming a 1-2 year delay is a success. (5/n) bsky.app/profile/nucl...
- Ignatius is also inconsistent. Back in 2015, while generally supportive of the Iran Deal, he argued its 10-year timeframe (again, misleading) meant Obama was making a "big bet." Now, an attack with much shorter-term effects is a success. (6/n) washingtonpost.com/opinions/aft...
- Ignatius's oped is written as if it's a news story. The "news" in this case is that--SURPRISE!--an Israeli source backed up claims by the Israeli government! (3/n) x.com/james_acton3...
- In fact, the source is actually walking back earlier Israeli claims! Previously, Netanyahu said Iran's program had been set back 2-3 years. Now Israel is saying 1-2 years. (4/n) washingtonpost.com/national-sec...
- First off, here's the link to my @foreignpolicy.com piece. (2/n) foreignpolicy.com/2025/07/25/i...
- 🎶When you attend a funeral, It is sad to think that sooner orl… …ater, those you love will do the same for you. And you may have found it tragic, Not to mention other adjec.. …tives to think of all the weeping they will do. 🎶 RIP, Mr Lehrer.
- Me in @foreignpolicy.com. The Trump administration's claim that Iran would need "years" to rebuild its previous nuclear program is like asserting that an unlocked bank vault would be impervious to a cyberattack. It’s true but misses the point. foreignpolicy.com/2025/07/25/i...
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View full threadI know I'll be accused of war mongering by people who read just the first tweet, but to be clear, more bombing won't help. I'm not optimistic about preventing Iran from getting the bomb, but the best way forward is diplomacy. (4/n)
- Here's the link to the whole thing again. Please take a read! (5/5) foreignpolicy.com/2025/07/25/i...
- Iran could build the bomb in a year or so without rebuilding its previous nuclear program. The loss of Iran's declared enrichment facilities and uranium metal production lines were simply not the crippling blows claimed by the Trump admin. (2/n) bsky.app/profile/nucl...
- 🧵How much damage was done to Iran's nuclear program? An analysis of Friday's reporting of the U.S. government assessment. I'll focus on the @nytimes.com, which was clearer than the earlier but confused @nbcnews.com story. (1/n) www.nytimes.com/2025/07/17/u...
- Claims/implications that Iran may struggle to recover the highly enriched uranium that is probably sitting underground at Esfahan are just silly. Digging debris out of tunnel entrances really isn't hard. (3/n) Spice warning:🌶️🌶️🌶️
- 🧵How much damage was done to Iran's nuclear program? An analysis of Friday's reporting of the U.S. government assessment. I'll focus on the @nytimes.com, which was clearer than the earlier but confused @nbcnews.com story. (1/n) www.nytimes.com/2025/07/17/u...
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View full threadBottom line: If Iran decides to build the bomb--as opposed to rebuilding destroyed facilities--it could probably do so in a year or less. To make matters worse, there are no IAEA inspections and little prospect of their resuming. (11/n) www.politico.com/news/magazin...
- One final point: Some folks will assume I'm making an argument for renewed military action. I'm not. My point is that there is no military solution. Even if the odds aren't good, diplomacy remains the option most likely to succeed in preventing Iran from proliferating. (12/12)
- For years, advocates of strikes essentially argued that, because weaponization was easy, diplomacy could not be trusted to prevent Iran from proliferating. Now the same folks are arguing the exact opposite point. (9/n)
- The reality is this. Converting UF6 into uranium metal is pretty easy. It doesn't need a dedicated facility. In the 1940s, the U.S. developed the technique in a university using equipment from the 1920s. (10/n) www.armscontrolwonk.com/archive/1220...
- The survival of Iran's 60% HEU is a BFD. Iran has enough, on further enrichment, for a handful on bombs. And that enrichment, to ~90%, can be done very quickly with only a tiny facility--MUCH smaller than Fordow let alone Natanz. (7/n) bsky.app/profile/nucl...
- Recognizing this, U.S. officials have basically said, "we don't care if Iran has HEU. We destroyed its facility to produce uranium metal, without which its HEU is useless." lol. (8/n)
- Satellite imagery shows that Iran has cleared at least one tunnel entrance at Isfahan per @armscontrolwonk.bsky.social. Perhaps this tunnel isn't connected to the tunnels where the HEU is stored, idk. But reporters should be *asking* about this, not assuming. (5/n) www.cnn.com/2025/06/27/p...
- Unblocking tunnel entrances is not difficult. The technology needed is the bulldozer--which Iran has. There's a legitimate question about whether Israel and the U.S. can DETER Iranian removal, but the technical barriers to removal are essentially nonexistent. (6/n)
- Attempts to play down the survival of most or all of Iran's HEU are comical. It may be true that "only" the HEU at Isfahan is accessible--but that's almost all of it! (3/n)
- Moreover, this material is not buried under rubble. The tunnels at Isfahan were not collapsed (too deep) so the HEU will be just fine. That said, the U.S. may have attacked the tunnel entrances, which does raise questions about the material's accessibility. (4/n)
- U.S. officials continue to argue that it would take Iran years to rebuild the facilities that were hit. That seems right to me. But a key question is this: How long would it take Iran to build the bomb? (2/n)
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- Still, at least anonymous sources are now being honest about the real policy, even if the odds of success are not good.
