LOD, Israel—An Israeli defense contractor on Monday unveiled a remote-controlled armed robot it says can patrol battle zones, track infiltrators, and open fire. The unmanned vehicle is the latest addition to the world of drone technology, which is rapidly reshaping the modern battlefield. Proponents say such semi-autonomous machines allow armies to protect their soldiers, while critics fear this marks another dangerous step toward robots making life-or-death decisions. The four-wheel-drive robot presented Monday was developed by the state-owned Israel Aerospace Industries’ “REX MKII.” It is operated by an electronic tablet and can be equipped with two machine guns, cameras, and sensors, said Rani Avni, deputy head of the company’s autonomous systems division. The robot can gather intelligence for ground troops, carry injured soldiers and supplies in and out of battle, and strike nearby targets. It is the most advanced of more than half a dozen unmanned vehicles developed by Aerospace Industries’ …