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.

A single drone, which evaded Israel’s vaunted aerial defense system, slammed into a mess hall at a military training camp deep inside Israel, killing four soldiers and wounding dozens of others