Chronologically, the Gospel of the Kingdom was the very first public message that was proclaimed by the historic Jesus of Nazareth.
Through the years, though, the Gospel has always been considered to be the message of Salvation through faith in Him and His redeeming work through His death and resurrection, as detailed in the last message in the synoptic gospels, the best of which is reported in Matthew 28:18-20 - All authority in heaven and on earth has been given to me. 28:19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and the Son and the Holy Spirit, 28:20 teaching them to obey everything I have commanded you. And remember, I am with you always, to the end of the age.”
However, a closer look at the four narratives of Jesus' life, death and resurrection show the highest incidences of mentioning the supernatural as recounted in the scriptures: the existence and exorcism of demons, the healing of the sick, the revivification of dead people and other miraculous works.
The most quoted incident involving the devil is aptly detailed in Job, but other than that, it's mostly inter nation conflict, as a result of Israel's disobedience to the God of Abraham, Isaac and Jacob.
Paul was right on the button in describing the Kingdom in 1 Co 4:22 as best demonstrated in power.
And power they did have, as this is outlined in the book of Acts, all the way down to the 4th century, long after the apostles had been martyred and John dying on the island of Patmos. There is much documentation to this effect, including Augustine's laying an account of at least 16 miracles that he had known about, including one that he had witnessed of his own.
Sadly, this is a view that is either argued against or hesitantly examined by a greater portion of the body of Christian believers today, as if it was almost anathema to want to avail of this Kingdom power that the Lord Jesus had wanted believers to avail of. In the book of John, Jesus Himself had declared that: I tell you the truth, anyone who has faith in me will do what I have been doing. He will do even greater things than these, because I am going to the Father.
Truth to tell, in this day where we are fast approaching the day of His return, He may yet validate His own doubt about returning to find His disciples not working within the operational guidelines of the Kingdom that He sent them out to proclaim, simply because most of them argue against it. He may truly not find the faith He would have wished His followers to have when He returns, if that remains to be the case.
However, I take comfort in the teachings of several scholars that are beginning to recognize the truth of the Kingdom's power available to the body of believers and nowhere is it more detailed than in the book written by Prof. JP Moreland, in "The Kingdom Triangle". Since I bought the book, I've been reading, contemplating and renovating my perspectives on my own walk so as to better my spiritual formation and perhaps, one day, exercise the operational power of the Kingdom, given the opportunity to do so.
There is a coming Kingdom, that is true. However, the Lord Jesus also said that the Kingdom is here. Now.
If we seek it, we will find it. With all of our hearts and minds.