I added these critical facts based on new reporting, that impact the thesis of the LLRX Research Guide: Law of International Armed Conflict.  “The sheer size of Hamas’s underground networks may, once fully discovered, be beyond anything a modern military has ever faced. One of the last conflicts that involved a large amount of tunnel complexes was the Vietnam War. American forces and others faced some tunnel complexes that ranged up to forty miles in length and one of the most concentrated places of tunnels, near Saigon at Cu Chi, contained 130 miles of passageways…the scale of the tunnels in Gaza, the Israel-Hamas war is the first war in which a combatant has made its vast underground network a defining centerpiece of its overall political-military strategy.” The source is this article by John Spencer, published on the Modern War Institute at West Point site, January 18, 2024. I have snipped a key portion but urge you to read the article in its entirety.

• Before the Israel-Hamas war, both the presence of Hamas tunnel networks and their growth over the years were very well known. The network was referred to as Gaza’s “Metro” or “lower Gaza.” The Israel Defense Forces (IDF) and scholars estimated before the war that there were three hundred miles of tunnels ranging from fifteen feet to over two hundred feet below the surface. The estimates were wrong.
• After three months of close combat and discovering over 1,500 tunnel shafts and underground passages, the IDF has learned enough to require the estimates to be revised. Israeli forces have unearthed massive invasion tunnels two and a half miles long, underground manufacturing plants, luxury tunnels with painted walls, tile floors, ceiling fans, and air conditioning, and a complex, layered, labyrinth underneath all areas of Gaza. The new estimates say the network may include between 350 and 450 miles of tunnels, with close to 5,700 separate shafts descending into hell.
• New estimates also indicate the construction of this subterranean network could have cost Hamas as much as a billion dollars. The group has poured resources over fifteen years not just into constructing tunnel passages, but for blast doors, workshops, sleeping quarters, toilets, kitchens, and all the ventilation, electricity, and phone lines to support what amount to underground cities. As much as 6,000 tons of concrete and 1,800 tons of metals have been used in this subterranean construction.
• The sheer size of Hamas’s underground networks may, once fully discovered, be beyond anything a modern military has ever faced. One of the last conflicts that involved a large amount of tunnel complexes was the Vietnam War. American forces and others faced some tunnel complexes that ranged up to forty miles in length and one of the most concentrated places of tunnels, near Saigon at Cu Chi, contained 130 miles of passageways…”