 The growing use of tunnels and underground facilities (UGF) by military and irregular forces to gain a tactical advantage is becoming more sophisticated and increasingly effective, making the likelihood of US Forces encountering military-purposed subterranean structures on future battlefields high.The Middle East is full of ancient and modern underground systems that can be used as assets for the enemy forces.In the US, both the northern and southern borders of the nation have had tunnels discovered connecting the US to Canada and Mexico being used by criminal elements for human smuggling, drug running, and other illegal activities.