In the final part of this conversation, Major John Spencer breaks down the discipline he's built his career on: urban warfare. He explains why cities are the most complex environment any military can fight in, why the U.S. lacks real expertise in fighting underground, and how history's most costly urban battles keep repeating the same avoidable mistakes. He closes by discussing what he sees as the next frontier of warfare — the world beneath our feet.Learn more about your ad choices. Visit podcastchoices.com/adchoices