The “Gospel of the Kingdom” is mentioned in Matthew 4: 23 , 9:35 , and 24:14. The “Gospel of Peace” is mentioned in Romans 10:15, and Eph 6:15. Do you think one is more for the Church age of Grace, and possibly the other more for the tribulation period? I’m really enjoying your website.
Gospel is an old English word meaning “good news,” the phrase both Jesus and Paul actually used. In Matthew, Jesus was speaking to Jews who were 483 years into a 490 year period prophesied in Daniel 9:24-27 at the end of which their Kingdom would be restored. Like some folks today, they didn’t see the 2000 year gap between the first 483 years and the last 7. Even after the Lord’s resurrection one of the first questions His disciples asked Jesus was if He was now going to restore the Kingdom. (Acts 1:6) The good news of the Kingdom is a phrase they understood.
Paul’s phrase, gospel of peace, is actually borrowed from Isaiah 52:7 which also refers to the Kingdom Age. It’s not until the Kingdom comes and the Lord’s reign begins that Earth will finally experience a time of peace.
But Paul also refers to the peace that exists between the Lord and His people now, because of the cross. “For He Himself is our peace.” (Ephes. 2:14) And so even in a hostile world where wars and rumors of war abound, we can feel the peace that surpasses all human understanding. (Phil. 4:7)
So the terms Gospel of Peace and Gospel of the Kingdom can represent two phases of the same Kingdom. Phase one is the Church age, where the Lord reigns spiritually in the hearts of His people. (The Kingdom of God is within you) Phase two is the Kingdom Age or Millennium, where He reigns physically over all the Earth. (The Kingdom of God is among you)
Both these parenthetical statements are legitimate interpretations of Luke 17:20-21 confirming a two phased Kingdom.