Today's D Brief: Russian airbase struck?; Danes fire defense chief; Army’s cutting-edge brigades; DOD’s software snafu; And a bit more.

Ukraine says it destroyed at least half a dozen Russian military aircraft in an overnight drone attack on the Morozovsk airbase in western Russia, which is believed to host Sukhoi Su-24 and Su-24M aircraft. About 20 personnel were allegedly killed in the attack, Ukrainian intelligence officials told the Associated Press. 

• Purported video of the attack’s aftermath was posted to social media, here. 

Moscow news outlets have not confirmed the destruction, but the state-run RIA news agency claimed air defense personnel shot down 53 Ukrainian drones overnight, with 44 of those targeting the Rostov region where the airbase is located, according to Reuters. 

Ukrainian intelligence officials worked with army troops to conduct the attack, according to AP, which noted, “If true, the attack would be among Ukraine’s most successful cross-border strikes.” Read more at CNN or the BBC. 

Developing: The U.S. Army is sending troops and equipment to Europe for the service’s largest exercise on the continent, DEFENDER 24, which began Thursday and runs through the end of May. The drills consist of three sub-exercises—Saber Strike, Immediate Response, and Swift Response—will link up with a larger NATO exercise referred to as Steadfast Defender 24, which the alliance says is its largest exercise since the Cold War, featuring “over 90,000 troops from all 32 NATO allies.”

Welcome to this Friday 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 1951, Ethel and Julius Rosenberg were sentenced to death for spying for the Soviet Union.

Denmark fired its top military officer this week after one of its vessels experienced a weapons malfunction four weeks ago while supporting the U.S.-led Operation Prosperity Guardian in the Red Sea. The crew’s resulting adjustments cost them so much ammunition the commanding officer elected to leave the region early in order to resupply. 

The first problem: Crew on board the frigate Iver Huitfeldt shot down four aerial drones while guarding commercial vessels in the dangerous waterway off the coast of Yemen on March 9. However, the frigate’s 76mm deck gun reportedly suffered a glitch during the engagement, which resulted in roughly half the rounds that targeted the drones detonating almost immediately after exiting the muzzle, according to local Danish defense outlet Olfi. 

“All shells in standard combat equipment are more than 30 years old, they have been retrofitted with a '2005 proximity fuze,” and that fuze “appears to be unsuitable for actual combat,” the commanding officer Sune Lind said in a message leaked to Olfi. Fortunately, “The crew switched to a backup radar and worked around the problem…but their most capable top-end radar remained unusable for half an hour,” the niche outlet Maritime Executive reported Wednesday. 

You can observe the Danes downing those drones in a video posted to social media Thursday, here. 

The second problem: Top officer Gen. Flemming Lentfer reportedly did not explain the situation in sufficient detail to his boss, Defense Minister Troels Lund Poulsen. What’s more, “the issue has been known for years without the necessary sense of urgency to resolve the problem,” Lind said, according to Olfi. 

However, “At no time during the engagement were we left defenseless,” Lind told Reuters on Thursday. “We had redundancies on board, so we were able to continue fighting and neutralizing the threats,” he added. 

But that’s not it for the Danes’ naval malfunctions this week, Reuters notes. “Separately, an activated but faulty missile launcher on another Danish navy vessel docked next to Iver Huitfeldt on Thursday triggered the closure of airspace and shipping traffic in the Great Belt strait, one of the world's busiest sea lanes and the main maritime access to the Baltic Sea.” A bit more, here. 

U.S. forces near Yemen destroyed a Houthi anti-ship missile prior to launch Thursday afternoon. “It was determined that the missile presented a threat to U.S. and coalition forces and merchant vessels in the region,” defense officials at Central Command said Thursday.  

Meet two brigades leading the Army’s charge toward cutting-edge tech: One is the 2nd Infantry Brigade Combat Team of the Hawaii-based 25th Infantry Division is putting commercial drones at the core of every operation, a program that got a boost in the Army’s recent budget submission. The second is the Europe-based 2nd Cavalry Regiment is experimenting with cutting-edge software and other tech, including virtual reality, that increases units’ ability to survive on a modern battlefield. D1’s Sam Skove talked with both, here.

Idea: How to fix the military’s software SNAFU—in particular, the one that has the Pentagon distributing code riddled with vulnerabilities. That’s from John Speed Myers, a former In-Q-Tel and RAND analyst who now leads an open source security team at Chainguard. Read his argument, here.

And lastly this week: Our Genius Machines event is back! Join Defense One’s Science and Technology Editor Patrick Tucker on Monday, April 8, at 2 p.m. as he talks AI with Kimberly Sablon (principal director for Trusted Artificial Intelligence and Autonomy, Office of the Assistance Secretary of Defense for Critical Technologies) and Emelia Probasco (senior fellow, Georgetown’s Center for Security and Emerging Technology). Register here (it’s free).