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This article was published 20/12/2013 (1009 days ago), so information in it may no longer be current.
WASHINGTON -- For more than a decade, the United States has targeted insurgents from the sky with increasingly advanced drones. But that may be contributing to a new trend: foreign militaries are using tunnels and other underground networks to gain a tactical advantage.
The U.S. Army has requested industry's help in developing high-tech robotics, communications gear and other equipment. "The growing use of tunnels and underground facilities by military and irregular forces to gain a tactical advantage is becoming more sophisticated... making the likelihood of U.S Forces encountering military-purposed subterranean structures on future battlefields high," army officials said.
-- The Washington Post