Today's D Brief: Ukrainian dam breaks; S. Korea scrambles jets; Iran’s hypersonic reveal; Overheating F-35s; And a bit more.

A large dam on the Dnipro River ruptured on Tuesday morning, draining water from a key reservoir and flooding towns downstream in both Ukraine- and Russia-controlled territory. Both sides are accusing the other of breaching the dam, which has been under Russian control for months.

Evacuation and rescue efforts are underway for tens of thousands of people in affected areas, which include the port city of Kherson in southern Ukraine. NPR’s science correspondent Geoff Brumfiel has written a detailed backgrounder explaining the stakes of the dam’s collapse, via Twitter, here.  

The reservoir created by the dam, which held roughly as much water as Utah’s Great Salt Lake, supplies much of Crimea’s population and agriculture. Already, “the canal which has traditionally met most of Crimea's water needs is receiving drastically less water,” Reuters reported, citing Kremlin statements.

The water is also used to cool the Zaporizhzhia Nuclear Power Plant, which has been all but shut down during the war. Experts told The Guardian that the lone operating reactor at the plant has enough cooling reserve to last several months, but that the loss of the reservoir may affect the ability to bring the other five reactors out of cold storage.

Watch video:

• Water flowing through the breached dam, via New York Times. 
• Flooded neighborhoods and other areas, released by Ukraine and Russia, at The Guardian.

NATO’s Jens Stoltenberg: “The destruction of the Kakhovka dam today puts thousands of civilians at risk and causes severe environmental damage. This is an outrageous act, which demonstrates once again the brutality of Russia’s war in Ukraine.”

“It is the children, women and men of Ukraine who will suffer the consequences of the terrible destruction of the NovaKakhovka hydroelectric power plant," said Roberta Metsola, president of the European Parliament, on Twitter. She added, “This is an act against humanity. A war crime which we cannot leave unanswered.”

Back stateside: Danish Prime Minister Mette Frederiksen dropped by the White House on Monday, where she and President Joe Biden “discussed our unwavering support for Ukraine” as well as their “shared work to bolster economic prosperity, increase energy security, and address the impacts of climate change,” according to the White House. 

Worth noting: NATO needs a new leader soon. And Frederiksen is among the few officials mentioned publicly so far as a potential successor to eventually outgoing NATO Secretary-General Jens Stoltenberg, whose original four-year term has already been extended three times for a total of nine years on the job, which is the second-longest in alliance history. Norwegian newspaper VG first dropped Mette’s name as potential NATO chief in late April. But on Friday, the Washington Post tossed British Defense Minister Ben Wallace’s name in the running for the alliance’s top spot. 

Compared to Frederiksen, the UK’s Wallace has struck a more openly defiant tone toward Russian aggression in Europe. Yet Denmark under Frederiksen has been among the most involved and ready NATO members helping contribute weapons to Ukraine. She’s also been particularly active in shoring support for Ukraine and the alliance among Nordic and Baltic nations since Denmark’s location positions it uniquely as a kind of gateway to the Baltic Sea, which is an especially vital lifeline for the Russian port city of St. Petersburg as well as the Russian exclave of Kaliningrad. 

When asked about the NATO job Monday at the White House, Frederiksen replied, “I have said before that I am not a candidate for any other job than the one I have now, and this has not changed after my meeting with the U.S. president.” 

“Nowadays, when war has returned to our continent, in Europe, it is so important that our allies and our friends, that we stick together, that we are united,” she said while seated beside Biden in the Oval Office on Monday. “And we have truly been for now 15 months, in Ukraine. We will, of course, continue, from a Danish perspective, our very strong support to Ukraine, but I’m looking forward to work[ing] even closer with you on defense and securities.”

NATO’s Stoltenberg is visiting Hungary today for discussions with President Katalin Novák. Hungary, you may recall, is among just two alliance members who have not yet ratified Sweden’s accession to NATO. The other nation is Turkey, which Stoltenberg visited over the weekend for discussions on just that topic with recently re-elected President Recep Erdogan in Ankara. 

By the way, NATO military operations are especially busy along its northern flank this week, Hans Kristensen of the Federation of American Scientists tweeted Tuesday. That involves the “Largest-ever air exercise Arctic Challenge over Nordic countries,” the staging of a “US aircraft carrier battle group off northwest Norway,” and the BALTOPS exercise currently underway in the Baltic Sea. “Can’t recall such intensity since [the] Cold War,” Kristensen said. 

Reminder: The annual NATO summit is just about one month away. It’s being hosted this year in the Lithuanian capital of Vilnius beginning July 11. Details, here. 

Welcome to this Tuesday edition of The D Brief, brought to you by Ben Watson and Bradley Peniston with Caitlin Kenney. On this day 79 years ago, the allied invasion of Nazi-occupied Normandy, France, began. 

Iran: We have a hypersonic missile. The newly announced Fattah ballistic missile can hit Mach 14 and fly 1,400km while maneuvering to “bypass the most advanced anti-ballistic missile systems of the United States and the Zionist regime, including Israel's Iron Dome," Iran's state TV said.
The unveiling comes a year after Iranian state media announced that it had built a hypersonic ballistic missile that could can maneuver in and out of the atmosphere. Reuters has a bit more, here.

S. Korea scrambled jets to meet China-Russia joint air patrol that entered its air defense zone to the south and east of the Korean peninsula. The patrol, which included four Russian and four Chinese military aircraft, was the countries’ first over the Sea of Japan and East China Sea since November, and the sixth since 2019, Reuters reported. China's defense ministry said the patrol was part of the two militaries' annual cooperation plan. 

F-35s are running hot, and each of the U.S. services that operates the plane formerly known as the Joint Strike Fighter gets to choose its own cooling fix. That’s all but certain to boost the price tag, reports Defense One’s Audrey Decker, here.

And lastly today: The Marines have picked a new top enlisted leader. Sgt. Maj. Carlos Ruiz is to succeed Sgt. Maj. Troy Black, who has held the position since July 2019, service officials announced Monday. The posting, which is largely responsible for morale and discipline issues and is personally selected by the commandant, chiefly serves as an advisor to that commandant—who, in this case, is outgoing Gen. David Berger, whose four-year term as service chief expires next month.
A bit more about Ruiz: He’s a native of Phoenix and he’s served in the Corps for 35 years, since he signed up in 1993 at the age of 18. He began his career as a warehouse clerk, and later became a recruiter and a drill instructor. He’s currently the senior enlisted leader for the U.S. Marine Corps Forces Reserve and U.S. Marine Corps Forces South.
Next: Ruiz is to assume his new assignment during a ceremony Aug. 8 in Washington. Read more about him and his assignment history, via the Corps, here.