In late 2023, Israel was aiming to assassinate Ibrahim Biari, a top Hamas commander in the northern Gaza Strip who had helped plan the Oct. 7 massacres. But Israeli intelligence could not find Mr. Biari, who they believed was hidden in the network of tunnels underneath Gaza.

So Israeli officers turned to a new military technology infused with artificial intelligence, three Israeli and American officials briefed on the events said. The technology was developed a decade earlier but had not been used in battle. Finding Mr. Biari provided new incentive to improve the tool, so engineers in Israel’s Unit 8200, the country’s equivalent of the National Security Agency, soon integrated A.I. into it, the people said.

Shortly thereafter, Israel listened to Mr. Biari’s calls and tested the A.I. audio tool, which gave an approximate location for where he was making his calls. Using that information, Israel ordered airstrikes to target the area on Oct. 31, 2023, killing Mr. Biari. More than 125 civilians also died in the attack, according to Airwars, a London-based conflict monitor.

The audio tool was just one example of how Israel has used the war in Gaza to rapidly test and deploy A.I.-backed military technologies to a degree that had not been seen before, according to interviews with nine American and Israeli defense officials, who spoke on the condition of anonymity because the work is confidential.

In the past 18 months, Israel has also combined A.I. with facial recognition software to match partly obscured or injured faces to real identities, turned to A.I. to compile potential airstrike targets, and created an Arabic-language A.I. model to power a chatbot that could scan and analyze text messages, social media posts and other Arabic-language data, two people with knowledge of the programs said.