The Bible refutes Watchtower teaching that Christ became king in 1914.
Biblically speaking, Jesus was enthroned immediately after His ascension. People in the first century were being transferred into Christ's kingdom. As Paul writes in Colossians 12 Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light: 13 Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son: Col.1:13-14