Folks like to cite Tertullian to argue for Catholic trinity because he was the first to use the term ‘trinitatem’. He did not, however, teach that God became a man, but that God SENT His Son, The Word. Those who cite the earlier ‘church fathers’, some of whom were already turning aside from truth, and Paul pointed some of them out in his letters, cannot find a place where they dare to call “Jesus”, “God”. Tertullian didn’t even do that.
What they fail to cite, however, is that the Catholic Church rejected Tertullian’s teaching, and indeed Tertullian himself was “anathema” to the ‘church’ that created the Trinity Doctrine, because he taught that the Son was SUBORDINATE to the Father, and so was the Spirit. This violates the doctrine of the Trinity.
Many protestants who think they are ‘Trinitarians’ actually are not; they’re just afraid of the Catholic Church and the spirit of Anti Messiah such that they won’t let go of the term. The Spirit of Anti Messiah denies that Yeshua is coming in FLESH, in a flesh and bone Body, to return to earth to rule. That is the colossal struggle we are in, to get the message of the Risen Savior to those who realize they need a willing sacrifice to die for them. Yeshua did that. And then God His Father raised Him from the dead, and sent His Spirit to those who would put their trust in that alone.