U.S. Army leaders say the next war will be fought in mega-cities..In 2017, the Army launched an accelerated effort that funnels some $572 million into training and equipping 26 of its 31 active combat brigades to fight in large-scale subterranean facilities that exist beneath dense urban areas around the world....For this new type of warfare, infantry units will need to know how to effectively navigate, communicate, breach heavy obstacles and attack enemy forces in underground mazes ranging from confined corridors to tunnels as wide as residential streets. Soldiers will need new equipment and training to operate in conditions such as complete darkness, bad air and lack of cover from enemy fire in areas that challenge standard Army communications equipment...
"This training circular is published to provide urgently needed guidance to plan and execute training for units operating in subterranean environments, according to TC 3-20.50 "Small Unit Training in Subterranean Environments," published in November 2017.
The Army has always been aware that it might have to clear and secure underground facilities such as sewers and subway systems beneath densely-populated cities. ..An assessment last year estimates that there are about 10,000 large-scale underground military facilities around the world that are intended to serve as subterranean cities...The endeavor became an urgent priority because more than 4,800 of these underground facilities are located in North Korea, the source said... But in addition to its underground nuclear missile facilities, North Korea has the capability to move thousands of troops through deep tunnels beneath the border into South Korea, according to the Army's new subterranean manual.
"North Korea could accommodate the transfer of 30,000 heavily armed troops per hour," the manual states. "North Korea had planned to construct five southern exits and the tunnel was designed for both conventional warfare and guerrilla infiltration. Among other things, North Korea built a regimental airbase into a granite mountain."
For its part, Russia inherited a vast underground facilities program from the Soviet Union, designed to ensure the survival of government leadership and military command and control in wartime, the manual states. Underground bunkers, tunnels, secret subway lines, and other facilities still beneath Moscow, other major Russian cities, and the sites of major military commands. More recently, U.S. and coalition forces operating in Iraq and Syria have had to deal with fighters from the Islamic State of Iraq and Syria operating in tunnel systems.
Toxic air, or a drop in oxygen, are other challenges soldiers will be likely to face operating deep underground. The Army is evaluating off-the-shelf self-contained breathing equipment for units to purchase."Protective masks without a self-contained breathing apparatus provide no protection against the absence of oxygen," the subterranean manual states. " Soldiers can find themselves exposed to smoke, carbon monoxide, carbon dioxide, hydrogen sulfide, methane natural gas underground, according to the manual. Breathing gear is expensive; some apparatus cost as much as $13,000 apiece, the source said.
Underground tunnels and facilities are often lighted, but when the lights go out, soldiers will be in total darkness. The Army announced in February that it has money in its fiscal 2019 budget to buy dual-tubed, binocular-style night vision goggles to give soldiers greater depth perception than offered by the current single-tubed Enhanced Night Vision Goggles and AN/PVS 14s.
Excerpts from Matthew Cox, Army Is Spending Half a Billion to Train Soldiers to Fight Underground, Military.com, June 24, 2018
See also DARPA on Underground War