 Examples are the defense of the Adzhimushkay quarry, or the use of Odessa Catacombs during guerilla warfare by Soviet partisans.In 21st century the issue of readiness to subterranean warfare was raised before the U.S. military in view of the tunnel tactic of Hamas.A December 11, 2013 RFI (request for information) titled "Technologies to enhance warfighter capabilities in subterranean environments" states in part