KYIV, Ukraine—Ukraine’s spectacular drone attack on Russia’s strategic bomber fleet on Sunday began with a daunting request from Ukraine’s president to his spy chief in late fall 2023.

Ukraine said its “Operation Spiderweb” attacked Russian warplanes worth hundreds of millions of dollars, utilizing drones that each cost under $1,000 and were launched from wooden containers carried on trucks.

Across the country, swarms of small explosive drones descended onto military bases and destroyed a large part of Russia's nuclear bomber fleet. The flying bombs were smuggled into Russia by Ukrainian intelligence services in a plot known as Operation Spiderweb.