Israel has one of the world’s best defenses against missiles and rockets, but struggles to detect slower-moving unmanned aircraft, experts said.

TEL AVIV, Israel — One of the worst mass casualty strikes on Israel in a year of war came not from dozens of Iranian ballistic missiles nor the repeated barrages of rocket fire launched by Hamas and Hezbollah. Instead, it was a single drone.

The day of the attack, the U.N.'s peacekeeping force said an Israeli tank broke down the entrance of its base in Lebanon.