What does Isaiah 45:1 mean?

This is what the Lord says to Cyrus, his chosen one, whose right hand he holds tight. God will bring down nations in front of him, strip kings of their power, open doors that no one can shut. Isaiah 45:1 - Modern Text Bible

(God is speaking directly to Cyrus, promising to give him victory over other nations and to remove any obstacles in his way. God is the one making this happen, not Cyrus’s own strength.)