Today's D Brief: Ukraine’s Avdiivka pullout; Houthis’ robot sub; US vetoes ceasefire resolution; V-22 crash investigation; And a bit more.

The Iran-backed Houthis in Yemen claim to have shot down a U.S. drone on Monday. If confirmed, it would be the third time Iran-backed militants have downed an MQ-9 Reaper since Hamas launched its war against Israel in early October, triggering attacks against U.S. forces across the Middle East, from Iraq, Syria, Jordan, and off the Yemeni coast. (The two other recent occurrences took place Nov. 8 near Yemen, and again on Jan. 19 when militants in Iraq shot down another MQ-9.) 

Here’s a purported video of the Monday strike, which happened over the western Hodeidah region of Yemen, according to the Houthis. U.S. officials told the New York Times on Monday that they had indeed lost a drone near Yemen, but they stopped short of elaborating. The missile used Monday is believed to be the same Iran-made “358” used previously by the Houthis and confiscated in Iraq. 

The Houthis also attacked and scuttled a Belize-flagged cargo ship, MV Rubymar, using anti-ship ballistic missiles on Monday. That attack occurred around 10 p.m. local time Sunday night, officials at the Tampa-based Central Command said Monday. “The ship issued a distress call and a coalition warship along with another merchant vessel responded” and transported the crew “to a nearby port by the merchant vessel,” according to CENTCOM. “The ship had turned off its Automatic Identification System tracker while in the Persian Gulf early this month,” the Associated Press reported Monday. It’s unclear what the ship was carrying on its route to Bulgaria from the UAE. 

The Houthis are also believed to have used drones to attack at least two other ships on Monday: one bulk carrier near the Gulf of Aden that seems to have escaped; and a second vessel closer to the Djibouti coast Monday evening, according to British maritime authorities. The latter attack resulted in only “superficial damage,” which did not alter the ship’s course or harm its crew, British officials said.  

And in a new first, the Houthis prepared an unmanned submarine to attack ships off Yemen’s coast, U.S. defense officials alleged. The drone was spotted Saturday along with three three mobile anti-ship cruise missiles and a drone boat, CENTCOM announced Sunday. U.S. forces destroyed the drone sub and the four other items in five different airstrikes at undisclosed locations across Yemen on Saturday. 

ICYMI: The U.S. Coast Guard intercepted a boat full of explosives, missile parts, and “unmanned underwater/surface vehicle components” in late January, CENTCOM said last week. More than 200 packages with these parts and more were found on the boat, and you can see some of that equipment in photos published Thursday. 

Among the notable details: “The photographs released show a propeller (screw) section that is consistent with UUVs used by Iran,” H.I. Sutton wrote Monday for the U.S. Naval Institute news. “Generally, these have a greater range than a torpedo but are slower, making them most effective against static targets such as ships in port or at anchor,” he writes. Read more, here

Related reading: 

Welcome to this Tuesday edition of The D Brief, brought to you by Ben Watson with Bradley Peniston. Share your newsletter tips, reading recommendations, or feedback for the year ahead here. And if you’re not already subscribed, you can do that here. On this day in 1939, the largest ever pro-Nazi rally in U.S. history was held at New York City’s Madison Square Garden. Six months later, Hitler invaded Poland, triggering the Second World War.

Is Israel’s occupation of Gaza and the West Bank since 1967 against international law? That’s the question before the United Nations’ highest court, which is hearing testimony this week from representatives of the Palestinians and dozens of other governments. “The proceedings, which were scheduled months before the war in Gaza began on Oct. 7, gained added urgency amid that conflict, the deadliest Israeli-Palestinian war,” the New York Times writes.

The court’s opinion will not be binding, and Israel has declined to testify. But the proceeding this time comes amid growing international pressure on Israel to halt fighting in Gaza, which began after Hamas-led attacks on Israel last October.” Read on, here

Elsewhere at the UN: US vetoes Arab-backed ceasefire resolution. CNN: “The US had already signaled its intention to veto the Algerian resolution, but has grown increasingly critical of Israel’s conduct in Gaza and on Monday proposed its own Security Council draft resolution calling for a ‘temporary ceasefire’ in the conflict.” The U.S. proposal “falls short of the wishes of most other Security Council members” yet indicates a growing dissatisfaction by the White House with Israel’s conduct of the war, CNN wrote.

NCS spox John Kirby: “We all wanna see this conflict end, but it’s gotta end in a way that leaves Israel safe from Hamas attacks,” and the resolution vetoed by the U.S. today did not make that possible, Kirby told reporters at a Tuesday press conference.

Israel raids Gazan hospital. Israeli officials say they arrested hundreds of militants at the Nasser Medical Complex in Gaza over the weekend. Doctors and medical staff at the hospital say they were taken outside, forced to strip to their underwear, and kept in the cold for hours while five were chosen to go back inside to care for patients. CNN reports.

The hospital has been turned into an Israeli military barracks, the Palestinian health ministry says. (ABC)

What caused the deadly Nov. 29 crash of a CV-22 tiltrotor off Japan? Air Force officials said they know what, but not why, and are declining to say more. “Engineering testing and analysis is ongoing to understand the cause of the material failure, a critical part of the investigation. Any disclosure of findings prior to investigations being finalized is premature and presumptive,” said a Tuesday statement from Air Force Special Operations Command.

It might be the aircraft’s propeller rotor gear box, CBS News reports, citing U.S. officials familiar with the preliminary findings. Eight airmen died in “the fourth fatal crash of the unique tiltrotor aircraft in less than two years. Twenty U.S. service members have died in the incidents, leading to a rare grounding in December of all Osprey aircraft by all branches of the U.S. military,” CBS wrote.

Ukrainian forces withdrew from the eastern city of Avdiivka on Saturday, handing Russia its only notable battlefield gain in nearly nine months. Russia’s invasion troops took control of the similarly destroyed city of Bakhmut in May. 

Ukraine withdrew from Avdiivka “because of congressional inaction,” John Kirby of the White House’s National Security Council told reporters Tuesday. House Republicans are still refusing to take up legislation to provide Ukraine additional funds for munitions and supplies, despite a bipartisan bill recently advancing in the Senate.

Why Avdiivka? The city would act as a logistics hub for Russian forces in occupied Ukrainian Donetsk, Kirby said. Whether the Russians can actually use this newly-occupied city in that way is unclear just yet. If Ukraine is not resupplied soon, Russia could use the city as a launch point for further invasion in the weeks ahead, he added. 

Kirby also said the U.S. will be unveiling a new sanctions package to hit various Russian officials following the recent death last week of jailed Russian opposition figure Alexy Navalny. Kirby was short on details, and said to expect more on Friday. 

And lastly today: Join several scholars and Russia-watchers marking two years of Russia’s Ukraine invasion with a livestreamed discussion this afternoon hosted by the Defense Priorities think tank, based in Washington. 

Emma Ashford of the Stimson Center joins Michael Kofman from the Carnegie Endowment for International Peace, as well as Ben Friedman and Daniel Davis from Defense Priorities. The event is slated for 12 p.m. ET. Details and RSVP here.