The Pentagon is preparing US military bases to operate autonomously for at least 90 days without outside support in the event of a large-scale war, Fox News reports. The new requirement is part of the military's Fortress Initiative, which aims to ensure that US forces can continue to fight even if the civilian systems they depend on are disrupted. “We do not want to rely on standard civilian urban infrastructure to support our national defense. We just can't. It's an unacceptable risk," Pentagon spokesman Sean Parnell told the channel.