The American newspaper *The New York Times* has disclosed these documents, shedding light on Hamas' preparations for a long-term conflict against Israel beneath the surface. According to the report, which also involved Yedioth Ahronoth journalist and ynet contributor Ronen Bergman, the details are based on documents captured by the IDF during the ground operation. Additionally, a war manual on tunnel warfare was reportedly found by Israeli security forces in the Zeitoun neighborhood of Gaza City in November, and Sinwar’s letter to the senior Hamas leader Mohammed Deif was captured in the same month in the southern part of the city.
The report indicates that while Israel was aware of Hamas' extensive tunnel network, it initially estimated its total length to be around 400 kilometers. However, based on the revelations during the war, this length is now believed to be potentially double.
Furthermore, the report reveals that just a year before the terrorist attack, Sinwar authorized an investment of $225,000 in armored doors that are resistant to explosions to protect the organization's tunnels from aerial bombardments and ground assaults. The seized training manual provides detailed instructions on how Hamas operatives should conduct underground combat, navigate in darkness, and fire automatic weapons within the tunnels to maximize casualties. The manual required Hamas commanders to measure down to the second how long it took their fighters to move between specific points in the underground tunnel system.
The IDF estimates that building a basic tunnel of nearly one kilometer costs Hamas about $300,000. The letter from Sinwar also indicates where the organization anticipated the most intense battles would occur: most of the funds were allocated for constructing armored doors in tunnels in northern Gaza and Khan Younis, two areas where some of the fiercest battles of the war indeed took place.
According to *The New York Times*, despite the detailed tunnel warfare tactics described in the manual, the IDF rarely encountered Hamas operatives behind the armored doors. When such doors were blown up, the operatives typically fled.