The book of Hebrews speaks of the Son as the Being through whom God created the worlds (Hebrews 1:2 Hebrews 1:2Has in these last days spoken to us by his Son, whom he has appointed heir of all things, by whom also he made the worlds;
American King James Version×) and who "sustains all things by his powerful word" (Hebrews 1:3, NRSV). Only God is great enough to do such things.

John confirms that Jesus was the divine Word through whom God created the universe: "All things were made through Him, and without Him nothing was made that was made" (John 1:3-14 John 1:3-14 [3] All things were made by him; and without him was not any thing made that was made. [4] In him was life; and the life was the light of men. [5] And the light shines in darkness; and the darkness comprehended it not. [6] There was a man sent from God, whose name was John. [7] The same came for a witness, to bear witness of the Light, that all men through him might believe. [8] He was not that Light, but was sent to bear witness of that Light. [9] That was the true Light, which lights every man that comes into the world. [10] He was in the world, and the world was made by him, and the world knew him not. [11] He came to his own, and his own received him not. [12] But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: [13] Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God. [14] And the Word was made flesh, and dwelled among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
American King James Version×).

Paul states quite clearly that "God ...created all things through Jesus Christ" (Ephesians 3:9 Ephesians 3:9And to make all men see what is the fellowship of the mystery, which from the beginning of the world has been hid in God, who created all things by Jesus Christ:
American King James Version×). He elsewhere writes of Jesus: "For by Him all things were created that are in heaven and that are on earth, visible and invisible, whether thrones or dominions or principalities or powers. All things were created through Him and for Him" (Colossians 1:16 Colossians 1:16 For by him were all things created, that are in heaven, and that are in earth, visible and invisible, whether they be thrones, or dominions, or principalities, or powers: all things were created by him, and for him:
American King James Version×). He adds in Colossians 1:17 Colossians 1:17 And he is before all things, and by him all things consist.
American King James Version×, "and in Him all things consist."

The Old Testament presents God alone as Creator of the universe (Genesis 1:1 Genesis 1:1In the beginning God created the heaven and the earth.
American King James Version×; Isaiah 40:25-28 Isaiah 40:25-28 [25] To whom then will you liken me, or shall I be equal? said the Holy One. [26] Lift up your eyes on high, and behold who has created these things, that brings out their host by number: he calls them all by names by the greatness of his might, for that he is strong in power; not one fails. [27] Why say you, O Jacob, and speak, O Israel, My way is hid from the LORD, and my judgment is passed over from my God? [28] Have you not known? have you not heard, that the everlasting God, the LORD, the Creator of the ends of the earth, faints not, neither is weary? there is no searching of his understanding.
American King James Version×). When the early followers of Christ say Jesus is the One through whom all things were created, they are clearly saying that Jesus is God.

Jesus claimed to be all that God is, and the disciples believed and taught it. They understood that Jesus was "the express [exact] image of His [God's] person" (Hebrews 1:3 Hebrews 1:3Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high:
American King James Version×) and "the image of the invisible God" (Colossians 1:15 Colossians 1:15 Who is the image of the invisible God, the firstborn of every creature:
American King James Version×), and that "in Him the whole fullness of deity dwells bodily" (Colossians 2:9 Colossians 2:9 For in him dwells all the fullness of the Godhead bodily.
American King James Version×, NRSV).

They understood precisely who He was and still is from His own words and actions. There was no question in their minds. They had seen Him prove it time and time again. They would go to their martyrdom firm in this conviction.