Left unresolved after an IDC conference on tunnel warfare on Monday was the question of what level of obligation Israel and the West have to warn civilians to evacuate tunnels when they attack guerrilla fighters’ underground networks.IDC professor and conference organizer Daphne Richemond-Barak explained the context of the dilemma. She said that, “the underground serves as the great equalizer. It reestablishes some symmetry between belligerents of unequal military capabilities to level the playing field.”In other words, one reason that Hezbollah and Hamas use tunnel warfare against Israel is to try to reduce the IDF’s overwhelming military advantages above ground.Richemond-Barak continued to say that “civilians are intentionally placed in danger by those digging tunnels in urban areas, from the very moment the tunnel is dug until it is fully eliminated.”Civilians are at risk from tunnel collapses or explosions near them – by the tunnel diggers, from water contamination and from being caught up as collateral damage in anti-tunnel strikes, she said.This last issue, the question of how much warning the IDF and the West must give to civilians when attacking guerrilla fighters hiding in tunnels in civilian areas, was hotly debated between international law experts Laurie Blank, Sasha Radin and others.Blank, a professor at Emory Law School, said that the first problem is that there is no obvious tool for even figuring out whether civilians are in a tunnel.While aircraft, drones and troops on the ground can perform surveillance to see whether civilians have evacuated a building above ground, those options are either unavailable or are much more difficult below ground.In addition, Blank said that whereas modern militaries have developed sophisticated matrices and calculations to evaluate the likelihood of civilian collateral damage above ground when attacking enemy combatants nearby, those calculations do not apply underground.She asked whether militaries are obligated “to go down and look. Proportionality requires that you gather information that is reasonably available. Is any information from a tunnel reasonably available? Do we need to reconsider our concept of what is reasonably available?“We cannot say just fire on tunnels and we cannot just say tunnels are off-limits when it is hard to know if civilians are there,” said Blank.Moreover, she asked – presuming there are civilians – “How do you warn civilians in a tunnel?”The implication from all of these questions was that as soon as you send forces down into a tunnel to check if there are civilians, or try to call down to civilians, you could both be risking the lives of your soldiers and giving the guerrilla fighters in the tunnels an easy opportunity to ambush your forces.While Blank did not directly say that Israel and the West can drop the need to warn civilians when it comes to tunnel warfare, she was clearly implying that the duty to warn could be significantly less than in above ground situations. In those situations, the IDF has used a variety of warnings to civilians to leave buildings in the line of fire, including telephone calls, dropping fliers and “roof-knocking” missiles designed to scare civilians out of an area without any deadly effects.In contrast, Rudin, from the Lieber Institute for Law and Land Warfare, seemed more circumspect.She said the fact that tunnels are underground “doesn’t change the legal requirements. You might need to interpret more and do more research, but the burden is to try to get more information.”Rudin noted that military experts have studied issues of the blast radius of different weapons and the impact of weather conditions above ground, suggesting that, “maybe they need to study how weapons work underground. The law is meant to be flexible and enduring.”Finally, she said that as people debate whether it is even possible to get additional information about civilians below ground, a top Defense Ministry official on tunnel warfare, referred to as Itai, had spoken on Sunday about technology advancing in unpredictable ways.Though Itai was referring to tunnel detection technology, Rudin was arguing that possibly new advances could be made to detect and warn civilians within tunnels.