Don't appear to use them because they're hidden. It's fairly common with drug smuggling I believe as well. And from what I remember there were tunnels from Pale

Don't appear to use them because they're hidden. It's fairly common with drug smuggling I believe as well. And from what I remember there were tunnels from Palestine to Israel. It's why Elon has said roughly that if you can detect tunnels being dug you should contact the military because you'll become rich; he said this at least once in reference to concerns that people in cities would feel The Boring Company tunnels being bored underneath their city - that you can't feel/notice it; obviously when breaching the surface you will. I've honestly wondered at times if industrious nations - who are arguably in contention with the ways of freedom and democracy - may be digging towards other continents, even if at current technology it would take 40+ years to make the journey. If you can all of a sudden deploy millions to 10s of millions of operatives and/or soldiers - even if it's a long journey, perhaps each with significant Bitcoin or perhaps cash in the currency of who you're invading, you might be able to very quickly takeover a large nation; or get a foothold, and arguably why the right to bear arms is additionally important - for domestic bad actors but foreign bad actors could in this scenario now be local.