Today's D Brief: S. Korea mulls going nuclear; Japan, US expanding military, space cooperation; China's personnel problem; And a bit more.

In a new first, South Korea’s new president says his country may consider building tactical nuclear weapons of its own if the North Korean nuclear threat continues to grow; and that latter possibility appears to be pretty likely at this point in North-South relations. “If that’s the case, we can have our own nuclear weapons pretty quickly, given our scientific and technological capabilities,” President Yoon Suk Yeol said Wednesday—while also cautioning this monumental change is not yet an official policy position, the New York Times reported from Seoul. 

For the record, “South Korea is a signatory of the Nuclear Nonproliferation Treaty, or NPT, which bans the country from seeking nuclear weapons,” the Times notes. Seoul’s leaders “also signed a joint declaration with North Korea in 1991 in which both Koreas agreed not to ‘test, manufacture, produce, receive, possess, store, deploy, or use nuclear weapons.’” But we all know how well North Korea has abided by that agreement. 

Not so fast? Nuclear proliferation academic Nicholas Miller of Dartmouth says you can mark him down as skeptical that this will happen. “If South Korea decided to go nuclear,” he wrote on Twitter on Thursday, “it would damage the NPT, trigger sanctions, threaten the alliance with the US, and provoke China and North Korea. Hence why I still tend to think it's unlikely and that these comments are for bargaining purposes.”

A second opinion: The “U.S. must be clear that extended deterrence and ROK nukes cannot coexist,” Ankit Panda of the Carnegie Endowment for International Peace tweeted Thursday.  

See also: 

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Welcome to this Thursday edition of The D Brief, brought to you by Ben Watson with Jennifer Hlad. If you’re not already subscribed to this newsletter, you can do that here. On this day in 1991, U.S. lawmakers authorized the use of military force to remove the invading Iraqi army from the neighboring nation of Kuwait. 

Defense Secretary Lloyd Austin welcomes his Japanese counterpart to the Pentagon this afternoon at around 4 p.m. ET. Austin and Defense Minister Yasukazu Hamada will be seeing each other for the second time in two days, following on the heels of the recent U.S.-Japan Security Consultative Committee meeting, involving the two countries’ military and foreign affairs chiefs, in Washington on Wednesday. “The Ministers welcomed the release of their respective National Security Strategies and National Defense Strategies, and confirmed unprecedented alignment of their vision, priorities, and goals,” the U.S. and Japan announced in a joint statement afterward.
China’s foreign policy is of particular concern, since Beijing’s leaders are seeking “to reshape the international order to its benefit and to employ China’s growing political, economic, military, and technological power to that end,” according to the statement. Such behavior “represents the greatest strategic challenge in the Indo-Pacific region and beyond,” the four officials warned.
New: The two countries are formally expanding cooperation in space, the Wall Street Journal previewed Wednesday. This means, in part, that “the U.S. is expanding the alliance’s security umbrella to safeguard Japanese satellites from attack, an undertaking previously given only to North Atlantic Treaty Organization allies,” according to the Journal. Tokyo and Washington’s top diplomats will travel to NASA headquarters on Friday to make these new changes officials. Tiny bit more from the State Department, here.
Also new and notable in U.S.-Japan defense: The Okinawa-based 12th Marine Regiment will soon transition into the 12th Marine Littoral Regiment by fiscal year 2025. Austin announced the change in a joint press briefing Wednesday, saying the U.S. “will equip this new formation with advanced intelligence, surveillance, and reconnaissance, as well as anti-ship and transportation capabilities that are relevant to the current and future threat environments.” No new units will be added to the Japanese island, the Marine Corps noted.
The 12th MLR will actually be the Corps’ second Marine Littoral Regiment—the first such unit was established in Hawaii in March of last year. Defense One’s Caitlin Kenney wrote about how these new units operate back in September. The Washington Post previewed the upcoming changes on Tuesday, here

In case you missed it Wednesday, Russia just changed the commander of its Ukraine invasion, which is a move the British military called “a significant development in Russian President Vladimir Putin’s approach to managing the war.” They also described it as “an indicator of the increasing seriousness of the situation Russia is facing, and a clear acknowledgement that the campaign is falling short of Russia’s strategic goals.”
The new commander is Chief of the General Staff Valery Gerasimov; and the prior war commander, Gen. Sergei Surovikin, is now one of three deputies under Gerasimov in the new role. “Surovikin has been widely praised” by Russian ultranationalists “for his championing of a more realistic approach” to the invasion and occupation of Ukraine. But “As a now deputy commander, his authority and influence is almost certainly hugely reduced,” the Brits say.
Wonk reax: Russia-watcher Mark Galeotti of the UK-based Royal United Services Institute said the new moves provide “Confirmation, if we needed it, that there will be serious offensives coming,” likely in the spring; “and that even Putin recognises that poor coordination has been an issue” for his invading forces. For Gerasimov, the new posting “is a kind of demotion, or at least the most poisoned of chalices,” Galeotti said. Success in the war is “now on him, and I suspect Putin has unrealistic expectations again.”
However, Galeotti cautioned, “In many ways, I don't think Moscow's strategy hinges anyway on battlefield victory; it's more about politics.” That is to say, Putin seems most intent “demonstrating to the West that Russia is in this for the long haul, and hoping that we will lose the will and unity to continue to support Kyiv,” according to Galeotti—who predicted “Putin will be disappointed, but he has to believe [that Ukraine’s supporters will peel away over time]; it’s his only real shot at some kind of victory.”
Wonk reax #2: “With Gerasimov in charge, if this is indeed permanent, I think the [possibility] of the Russians asking their tired force to do something that it cannot handle rises exponentially,” said Dara Massicot of the Washington-based RAND Corporation. “With this change, I view this as a power struggle that has resolved in favor of Shoygu/Gerasimov,” who have years of experience inside the Kremlin. After all, Massicot writes, “Seniors in Moscow are clingingly fiercely to the status quo and also [the] Soviet past. [It’s] important to keep in mind that they default to looking inwards and backwards even when it [leads] them to poor outcomes.”
Developing: Russia’s navy seems to have suddenly vacated one of its largest Black Sea ports in Novorossiysk, just a little bit east of Ukraine’s occupied Crimean peninsula. Naval enthusiast and author H.I. Sutton said Wednesday on Twitter that he noticed “A sudden mass exodus of warships and submarines from Novorossiysk. He described it as “very unusual,” and speculated it “may be a leading indicator of an operation of some kind.”
Additional reading: Russia Finds a New Target: Maps That Still Mark Crimea as Ukraine’s,” via the Wall Street Journal, reporting Thursday from Moscow.

And lastly today: One final goodbye to SecDef25 Ash Carter. The Washington National Cathedral is holding a memorial service for the former Pentagon chief this morning at 11 a.m. ET. President Joe Biden and Defense Secretary Lloyd Austin are expected to speak. State Secretary Antony Blinken will also be there, along with former Joint Chiefs Chairman retired Marine Gen. Joseph Dunford.
You can catch the livestream for that event over on YouTube, here.