"Defensively, Hamas will use tunnels to escape IDF observation and attack. Any Hamas military capability that survives Israel’s current air campaign will mostly be deep underground. Hamas will have already placed its leadership, fighters, headquarters, communication, weapons, and supplies like water, food, ammunition in its tunnel complexes to prepare for the ground assault by Israeli forces. The tunnels will allow fighters to move between a series of fighting positions safely and freely under massive buildings, even after the IDF drop thousand-pound bombs on them. Hamas tunnels often have generator power, air ventilation, water pipes, and stockpiles of food that will allow the group’s fighters to better withstand the most basic challenges, like normal exhaustion, that result from urban siege and isolation. Hamas leaders and fighters will use the tunnels to remain mobile to escape entire sections of the combat area when they feel they are about to be decisively attacked or surrounded. Importantly, Hamas has also dug a large portion of its tunnels under, and connected to, civilian sites like school, hospitals, and mosques in dense urban areas. Among other reasons for doing so, this is part of its defensive warfare strategy."
"Offensively, Hamas tunnels allow the group’s forces to conduct protected and surprise attacks. They will use the tunnels to infiltrate behind IDF positions to surprise Israeli forces that might not be as well prepared or equipped for combat as those spearheading the campaign, like those in logistical areas. Interconnected tunnels under urban areas will allow Hamas to move quickly between prepared attack positions with caches of sniper rifles, antitank munitions, rifle-propelled grenades, and other weapons and ammunition. Tunnels will be the vital element of Hamas’s guerrilla warfare strategy. Its fighters will form small hunter-killer teams that move underground, pop up, strike, and pop quickly back into a tunnel. Hamas also uses the tunnels to hide and move rockets. These rockets can be remotely detonated or transported to hidden launch sites at the last minute. Hamas will also have many tunnels rigged with hundreds of pounds of explosive to function as tunnel bombs under main roads and buildings that the IDF might be lured into."