Harmagheddon or the end of the world coming soon
I think that to be a 'witness' one had to believe and have faith in the good news regarding the establishment of God's kingdom in 1914 and the elevation of the 'Servant' mentioned in Isaiah to the throne of the Messianic Kingdom so that they could join with the anointed remnant in the preaching and so by doing be a witness.
As a witness and recognising Matthew 24:14 as being fulfilled all the other beliefs followed which included the appointment of the 'faithful slave class' and the role assigned to them.