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Dr. Jeffrey Lewis Profile picture
Dr. Jeffrey Lewis
@ArmsControlWonk
Professor at @MIIS, staff at @JamesMartinCNS & host of the @ACWpodcast. Member @theNASEM CISAC; former member @StateDept ISAB (2022-2025).
15 subscribers
Jun 23 • 17 tweets • 6 min read
Why am I so unimpressed by these strikes? Israel and the US have failed to target significant elements of Iran's nuclear materials and production infrastructure. RISING LION and MIDNIGHT HAMMER are tactically brilliant, but may turn out to be strategic failures. 🧵 1/17 Netanyahu's justification for conducting this strike was that "Iran has produced enough highly enriched uranium for nine atom bombs -- nine." He refers to Iran's stockpile of ~400 kg of 60% U-235 which, if further enriched, would be enough for 9-10 weapons. Let's consider. 2/17
Jun 19 • 12 tweets • 6 min read
References to "tactical" nuclear weapons in this otherwise great @guardian story by @hugolowell are misleading. The US would drop a strategic B61-11 nuclear earth penetrator with a yield of 300 or 400 kilotons. Hiroshima and Nagasaki were 15 and 21 kt.
theguardian.com/world/2025/jun…The effectiveness of GBU-57s has been a topic of deep contention at the Pentagon since the start of Trump’s term, according to two defense officials who were briefed that perhaps only a tactical nuclear weapon could be capable of destroying Fordow because of how deeply it is buried. Trump is not considering using a tactical nuclear weapon on Fordow and the possibility was not briefed by defense secretary Pete Hegseth and the chairman of the joint chiefs of staff Gen Dan Caine in meetings in the White House situation room, two people familiar with the matter said. ... Those in the briefing h... Here are the nuclear weapons in the US "enduring stockpile" from @ENERGY's stockpile management plant. Note that the B61-11 nuclear earth penetrator is labeled as a "strategic bomb" -- and for good reason.
energy.gov/sites/default/…Image
Jun 16 • 7 tweets • 3 min read
I see @SangerNYT asked why Israel hasn't hit the stockpile of enriched uranium. My understanding is that the hex is stored in the tunnels at Isfahan and Israel hasn't been able to destroy the hard, deeply buried targets. Thread. Image Isfahan UCF has some tunnels that are are about 100 m under a mountain that Israel has not yet tried to hit. The Iranians were pretty proud of these tunnels, which were constructed around the same time as Fordow by the same dwarves (aka the Passive Defense Organization). Image
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Jun 10 • 13 tweets • 6 min read
This is probably the the new North Korean uranium enrichment facility that @iaeaorg DG @rafaelmgrossi briefed the Board of Governors about. @sam_lair and I have a summary on the blog. Nice shot by our friends at @planet.
armscontrolwonk.com/archive/122048…Image Here is what @grossi said:
iaea.org/newscenter/sta…The undeclared enrichment facilities at both Kangson and Yongbyon are of serious concern. In addition, the Agency is monitoring the construction of a new building at Yongbyon which has dimensions and features similar to the Kangson enrichment plant.
Jun 2 • 14 tweets • 3 min read
Trump's offer to Iran, as reported by @BarakRavid, is a dollar-store-JCPOA.

The JCPOA -- which Trump abandoned -- had all of these provisions, usually in ways that were stronger or more carefully constructed.

He's trying to put Humpty Dumpty back together again. A thread. Image @BarakRavid Here is the original story. The proposal was "described to Axios by two sources with direct knowledge — one of whom provided a point-by-point breakdown." This is a paraphrase, so sometimes its hard to know what they are getting at.
axios.com/2025/06/02/ira…
Dec 12, 2024 • 7 tweets • 2 min read
A bunch of tankie accounts are reposting this claim that Russia can produce 25 Oreshnik IRBMs a month.

That's probably wrong. 🧵
militarywatchmagazine.com/article/ukrain… The claim of 25 missiles a month is falsely attributed to the @DI_Ukraine. What @DI_Ukraine says, according to other news outlets, is 25 IRBMs per YEAR, not per MONTH.
babel.ua/news/113282-ro…
Nov 20, 2024 • 23 tweets • 7 min read
Russia has issued a new (2024) "Fundamentals of the State Policy of the Russian Federation in the Field of Nuclear Deterrence" (основы Государственной Политики Российской Федерации В Области Ядерного Сдерживания). Same wine, new bottle. 🧵.
static.kremlin.ru/media/events/f… BLUF/TLDR: Four significant changes from 2020 but these changes are all (1) at the margin, (2) consistent with past Soviet/Russian policy, and (3) stuff that I believed was the policy in fact, even if it had been unstated.
Nov 14, 2024 • 20 tweets • 7 min read
No, it probably can't. At least not anytime soon. A short 🧵. 1. The report was written by a think tank, not technical experts from the 🇺🇦 gov't.
2. 🇺🇦 has ~7 tons of reactor Pu, enough for several hundred simple-fission weapons.
3. The Pu is sitting in spent fuel. To use it, 🇺🇦 would have to build a separation plant, which would take years and cost hundreds of billions.
web.archive.org/web/2024111318…
Nov 8, 2024 • 7 tweets • 3 min read
This is a great idea! If North Korea tests the Hwasan-31 "tactical" nuclear warhead, this is what we'll see. A short 🧵. According to Kim Yo Jong, the explosive power or "yield" of the Hwasan-31, pictured below, is the same as 900 tons of TNT -- that's much smaller than the bombs dropped on Hiroshima (15,000 tons) or Nagasaki (21,000 tons). Image
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Oct 4, 2024 • 5 tweets • 2 min read
I am coming around to the idea that Israel's stocks of Arrow-2 and -3 interceptors are either depleted from April or are being saved for more sensitive targets. A little thread on cost effectiveness at the margins. The US fired 12 interceptors during this engagement from the destroyers Bulkeley and Cole. Assuming they were SM-3 interceptors, that represents the production run for an entire year, at a cost of about $400 million total. (Each interceptor is about $30 million.) Image
Image
Sep 13, 2024 • 18 tweets • 8 min read
I think the three big takeaways are:
1. That's likely Kangson. It *is* an enrichment plant.
2. The centrifuges are more advanced than the ones Hecker described in 2010.
3. KCNA did not to show the plant staff or the control room. Someone read about STUXNET.
🧵 As @ColinZwirko reported, the @JamesMartinCNS OSINT team concluded last night that this facility was most likely the presumed uranium enrichment plant at Kangson. I spent the morning quadruple-checking. I think they're right.
nknews.org/pro/north-kore…
May 26, 2024 • 11 tweets • 7 min read
Our friends at @planet have a really nice series of images of the "Typhon" missile launchers that the US has temporarily deployed in the Philippines. A couple of observations. Image The Mid-Range Capability (MRC) or "Typhon" (named after a Greek giant just to please @tomkarako) is a @USArmy missile system capable of launching the ~500 km-range SM-6 and the ~2000 km-range Tomahawk missiles. There is a nice CRS report on the system.
crsreports.congress.gov/product/pdf/IF…

Image
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May 22, 2024 • 7 tweets • 3 min read
Russia conducted an exercise in which it practiced starting a nuclear war. A short thread.
iz.ru/1699925/2024-0… We get to see a convoy of Iskander vehicles -- a very rare security vehicle, some transloaders, some containerized missiles (ballistic and cruise) and some support vehicles. Image
Apr 14, 2024 • 5 tweets • 2 min read
After the US transmogrified Qasem Soleimani into his final form as a a parade float, Iran conducted a big missile strike against a US airbase in Iraq. Miraculously, no one else died.Did a whole pod ep on it.

Some implications for this morning. Season 2, Episode 5: The Worst Case Scenario (Almost)
middlebury.edu/deal-podcast Iran was prepared for a significant escalatory response by the US -- so much so that a jumpy Tor SAM crew shot down a civilian airliner (PS752) taking off from Tehran International Airport, killing all 176 people on board.
cnn.com/2023/04/17/mid…
Apr 13, 2024 • 7 tweets • 3 min read
A quick summary on Iran's drones, cruise missiles and ballistic missiles that can reach Israel. Reminder, Iran is about 2000 km from Israel. Image “Drones” usually means the Shahed-family of loitering munitions, like the -131/136 models that Iran exports to Russia. They are long-range, but only carry about 20 kg of explosives. (Not that I would want 20 kg of explosive dropped on my office, mind you.)
dia.mil/Portals/110/Do…
Mar 3, 2024 • 17 tweets • 5 min read
This is some amazing reporting, but I am unpersuaded by the framing. Russia's nuclear doctrine as described sounds exactly what official documents say it is. A short thread.
ft.com/content/f18e6e… In 2020, Putin signed a decree titled “Foundations of State Policy of the Russian Federation in the Area of Nuclear Deterrence.” @AnyaFink translated it for CNA at the time. So, we can compare the @FT story with it.
apps.dtic.mil/sti/pdfs/AD115…
Jan 5, 2024 • 11 tweets • 6 min read
The case for the Russian missile that struck Kharkiv on January 2 being a North Koran Hwasong-11 variant is a very, very strong. A short thread building on the work of the #OSINTatMIIS team, especially the amazing @DuitsmanMS.
politico.com/news/2024/01/0… A point of clarification. North Korea manufactures several variants of the Hwasong-11 including the Hwasong-11A (US designation: KN-23) and the Hwasong-11B (KN-24). We're still not sure which variant was used in the attack on Kharkiv. I made a chart to help you out.
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Nov 12, 2023 • 10 tweets • 3 min read
Color me skeptical. A short thread. The use of "ban" implies some sort of legal agreement. Biden can't manifest treaties in meetings with foreign leaders. We're more likely to get something akin to the 1998 US-PRC nuclear non-targeting agreement -- nice, aspirational and useless.
clintonwhitehouse4.archives.gov/WH/New/China/1…
Aug 21, 2023 • 18 tweets • 5 min read
Ok, we're on track to publish something on Ted Postol's analysis of North Korea's Hwasong-18 ICBM. But I wanted to do a short thread that illustrates just how incompetent Ted's analysis is.

I am aware of how this reads, but I’m not wrong. 😉 Ted says the Hwasong-18 is the Topol-M. So let’s start with some facts. The first stage of the Topol-M (RS-12M) is 1.86 m in diameter and 8.04 meters long. Russia had to declare this data under the START Treaty. Image
Jul 6, 2023 • 13 tweets • 6 min read
I don't understand what it means for an imaging satellite to have "no military utility." TBH, this feels like coping rather than rational analysis. A short thread.
en.yna.co.kr/view/AEN202307… The view attributed, but not sourced to, the US and ROK is that military utility is defined as being sub-meter resolution. This is very, very dumb thing to say. (This is so dumb that I can't believe this is an actual view of an actual human.)
May 17, 2023 • 21 tweets • 7 min read
Since I got dragged into this, a short 🧵. There are three separate issues here: (1) Do we take the Ukrainian claim to have downed 18 targets at face value, (2) is it likely and (3) does PAC-3 make a meaningful contribution to the defense of Ukraine? My answers: No, not likely, and still maybe.