Huge topic within libertarianism. You could start here: https://www.goodreads.com/book/show/7717015-the-private-production-of-defense https://www.goodreads.com

Huge topic within libertarianism. You could start here: https://www.goodreads.com/book/show/7717015-the-private-production-of-defense https://www.goodreads.com/book/show/7717015-the-private-prod...