When looking at History, Oneness are supported by scriptures, History, Grammar or Logic.
By scriptures we see p***ages supporting that there is One God, that God is one Lord, that Jesus is Lord and that God is the Father, that the Father was the only true God, that God is Spirit, that Spirit is invisible.
We further see from scripture that Jesus Christ was the anointed man, the Son of God a perfect sinless man and not God, but a flesh and bones human tabernacle.
Scripture is clear that men saw the Christ, they could not see the Father, but by seeing the Son, the body/express image.
God is called Father in scripture, God is not his own Son.
God the Father is invisible, the Son was visible.
Jesus stated 'Spirit hath not flesh and bones as you see me have" Luke 24:39
The Apostle John said "NO MAN HATH SEEN GOD AT ANYTIME", this shoots down the theory of the God, the Son of God.

Now History shows NO TRINITARIAN IN THE 1st or 2nd century.
Trinitarians try and claim the 1st century Bible writers, but they did not write the phrases that Trinitarians are forced to use to formulate the development of a Triad of three beings.
No Trinity, no three persons, no beings, no triune godhead.

In the 2nd century, one should find the continuation of a Trinity of this three being godhead, We don't though, just one God and not a three god spoken of.
One can search high and low and see no Trinity in this century, no person teaching that view.
It will not be termed Trinity till the 3rd century by the inventor of this religion Tertullian.
Tertullian in his writing 'Adversus Praxeas' stated in Chapter 3 that the majority in his day believed he taught two and three gods, not One God, he called these followers of the Monarchia.
They held as Praxeas the majority view which denied the economia or three in one of Tertullian.
In the 2nd century, the Monarchian Bishop Ignatius was counted by Virginia Corwin Historian as being Monarchian.
So where was the Trinitarians in this century? who do Trinitarians calim as their own, those who taught what they are bringing forth today?
Certainly not Justin Martyr, or Theophilus or Origen, but who?

Grammar supports Oneness Apostolics, God is One, not three, Holy one, not holy three, heis Theo=one God using the masculine one.
Though Trinitarians tried to change Echad to mean only a plural one, this is shot down as Adam had a echad rib and it wasn't speaking of a slab of BBQ ribs from his side.
Grammar in Matthew 28:19 supports Oneness when it says "name" and not names for the baptismal formula and then have all the p***ages in the Bible use "Jesus" Name.

Logic, now some think this means some trickery of a idea, but logic is not such, but Mathematical ideas proving that one idea is proven through logical mathematical equations, using writings from the Post Apostolic Fathers and scriptures, a great book on this is by Robert Herrmann in
Oneness, the Trinity and Logic.

So One God versus three gods , Oneness are Christians, Trinitarians are part of the Roman system of paganism, Mithraism, polytheism.