The purpose of this article is to examine how to establish a practical defense system against the ever-expanding cyber threats, focusing on the concept of total force used by the U.S. military. In particular, as cyberspace is growing in risk to the extent that it is called the fifth battlefield after land, sea, and space, in order to establish an all-out security posture, it is necessary to restructure reserve forces that have remained in support-oriented auxiliary resources. As an improvement direction, the introduction of a permanent power system for reserve forces in the field of cyber defense, which introduced the concept of the U.S. all-out policy, and the establishment of practical training programs necessary for cyber operations were suggested. Reserve power needs to be effectively re-established and rearranged in a large framework of security strategies, and should be further strengthened to cope with the cyber war expanding in the era of digital transformation.