Smoke rising over Kyiv, Ukraine, after a strike on Wednesday. It was the third major attack on the capital in a week.

“Frankly, we wouldn’t be able to afford 420,000 square feet in downtown San Francisco,” said Keith Miao, the founder of Birdstop, a drone start-up in Detroit.

The Locust, an anti-drone laser system that has been used recently along the border with Mexico, last month in Albuquerque, N.M.

A German soldier demonstrating a drone jammer on Friday. If Europe builds a “drone wall,” it will be not a physical barrier but a network of trackers.

Ukrainian flags and the flags of various brigades hanging at OKKO gas station in Kharkiv, Ukraine.

Ukrainian soldiers preparing to launch an assault in the Donetsk region last month. After more than 15 months of Russian offensive, they are finding opportunities for localized counterattacks.

Russian soldiers at an artillery position in the Kursk region, in December. Even before it sent troops, North Korea was supplying Russia with millions of artillery shells.

Drone hunting at Island Beach State Park in Lanoka Harbor, N.J.

Hezbollah said it had fired 100 rockets at military targets over the border with Israel as part of an “initial response” to the drone strike that killed a top commander.

A visualization of the rapidly-changing frequencies of the Himera military radio, which features signal-hopping technology that makes it difficult to jam.

Clearing debris on Monday after an overnight missile strike near an art museum in Odesa, Ukraine.

The Air Force’s pilotless XQ-58A Valkyrie experimental aircraft is run by artificial intelligence.