THE AGILE SECURITY DEVELOPMENT LIFE CYCLE (ASDLC) is a book designed to address the ongoing shortfalls and failures of "Secure System Development." The author seeks to use his over 20 years in the public and private sector program management and cybersecurity to create a solution. This book provides the first-ever integrated operational-security process to enhance the readers understanding of why systems are so poorly secured. Why we as a nation have missed the mark in cybersecurity? Why nation-states and hackers are successful daily? This book also describes the two major mainstream "agile" NIST frameworks that can be employed, and how to use them effectively under a Risk Management approach. We may be losing "battles, " but may be its time we truly commit to winning this cyber-war.