In addition to long-range artillery attacks on bridges and supply lines, there have been mysterious killings, fueling rumors that Ukraine is conducting a deep special forces operation behind enemy lines. That appeared to be confirmed on Saturday when unnamed Ukrainian soldiers told The Times that there was a broad network of insurgents operating in Russian-held territory in Kherson and Zaporizhzhia. “Kids from the south are preparing for 9/11,” said “Rebel,” 34, a former military intelligence officer who trains and leads party groups around the country. “We know all the traitors. We know everyone who helps the Russians. A big surprise and many gifts await them before that date.” It was not clear what the September date referred to.