TEL AVIV — Hezbollah began deploying small drones controlled by fiber-optic cables against Israeli forces along the northern Israel border during the round of fighting that began March 2. The Iran-backed Lebanese militant group announced the use of the fiber-optic guided drones for the first time in that period, having previously relied on other drone types for years.

The cables, roughly the width of dental floss, connect an operator directly to the drone rather than transmitting commands by radio. That direct link makes the aircraft impossible to jam electronically, allowing them to evade air defenses that can otherwise cause drones to crash or return to their point of origin. The drones are small, hard to track and potentially lethal, though wind or other drones can tangle the control cables.

"If you know what you're doing, it's absolutely deadly," said Robert Tollast, a drone expert and researcher at the Royal United Services Institute in London. Tollast said fiber-optic drone cables have been recorded extending as far as 31 miles (50 kilometers), though such drones do not have the same range as those that use radio links or artificial intelligence to navigate. He said Russia and Ukraine are using many different types of drones at a phenomenal scale, and footage from front-line Ukrainian towns shows them coated with shiny, fishing line-like strings resembling massive spiderwebs.

Hezbollah has mostly used the drones against Israeli soldiers operating in southern Lebanon or in towns on the border. Over recent weeks, the group has aired videos on social media platforms and on its Al-Manar TV station showing the attacks. One strike last weekend killed an Israeli soldier and wounded six others, some seriously, with Hezbollah issuing drone footage that showed the weapon exploding among troops gathered near a vehicle. A second drone fired at the same location narrowly missed a military helicopter landing to evacuate the wounded. On Tuesday, a fiber-optic drone attack killed an Israeli civilian contractor in southern Lebanon.

Israel has been adding nets and cages to military vehicles to defend troops. Ran Kochav, former head of the Israeli military's air defense command, said Israel has sufficient firepower to intercept drones but needs early detection, and that monitoring systems capable of tracking changes in light, identifying signals and recognizing the sound of drone propellers have not been widely deployed along the northern border. He said Israel should have monitored advances in fiber-optic drones in the war in Ukraine and had assumed other Iranian allies would eventually use them.

On April 13, a drone crashed into the backyard of Zevik Glidai's home in Kiryat Shmona, about 2 kilometers from the Lebanon border. Glidai, a 78-year-old math teacher and volunteer ambulance driver, and his neighbor extinguished the resulting fire with a garden hose and found the destroyed drone surrounded by loops and curls of white thread. "They picked up all of the pieces that they could pick up, and they left me a few optical fibers as a keepsake," Glidai said.