What is the periodic document that looks 20 years into the future called?

The correct choice refers to the document that outlines defense strategy with a long-term perspective, particularly focusing on a 20-year outlook. The Quadrennial Defense Review (QDR) serves as a comprehensive evaluation of the strategies and priorities of the Department of Defense every four years.

The significance of the QDR lies in its ability to assess contemporary challenges and envision the future needs of the military. It takes into account trends in global security, technological advancements, and potential threats, allowing for strategic planning that extends into the next two decades. This long-term focus is essential for preparing forces to meet evolving national security requirements and resource allocation decisions.

The other options do not capture this long-term vision. The National Defense Strategy, for instance, presents current strategic priorities and objectives but does not necessarily project far into the future like the QDR. Similarly, a Strategic Plan may outline specific initiatives or goals but typically lacks the overarching framework and evaluation of the broader defense landscape that is characteristic of the QDR. The Defense Operations Guide mainly focuses on immediate operational procedures rather than long-range strategic planning.