With the Reformation, Luther revived Augustine’s insights. The kingdom of Christ advances exclusively through the Spiritual sword: the Word of God. It is embraced by faith, rather than being coercively imposed by force. In earthly affairs, unbelievers often excel believers. We build temporal cities by our works, but receive the kingdom of Christ through preaching and sacrament.
Horton, Michael; The Gospel Driven Life: Being Good News People in a Bad News World; Baker Books; Grand Rapids, MI; Copyright 2009; page 251