Russian soldiers in Ukraine made worried calls home as their efforts in Ukraine faltered — but their loved ones weren’t the only ones listening.

Ukrainian forces used the cell phone calls made by Russian soldiers to locate them and wipe the troops out in large numbers, according to an investigation published by The New York Times that details Russia’s blunders throughout the war.

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“We listened to the Russian soldiers as they panicked and called their friends and relatives,” a Ukrainian official who leads the efforts to intercept the phone calls told The Times. “They used ordinary phones to make decisions about their further moves.”

Read more: yahoo