Before I answer your question, let me say on behalf
of our AskACatholic Team:
Thank you, Sir for serving our country and putting
you life in danger in order to keep us safe.
With respect to Genesis 1:26, I assume (by your
question) that you are talking about God referring
to Himself as "us" being a reference to
the Trinity. I think it's safe to say this
is an allusion to Triune nature of God. The Trinity
is actually never named, as such, in either the New
or the Old Testament. It is however, implicitly stated
from the very first verse of Genesis and throughout
the entire Bible.
Genesis 1 says in the beginning God (Elohim) created
the heavens and the earth.
The word Hebrew word Elohim which we translate
as God is a plural noun. In the next few verses,
we see that the Spirit or breath of God hovered over
the waters and then we read that God "spoke" every
time He created something, saying let there be ....
John's Gospel, mirroring Genesis 1, begins by saying
In the beginning was the Word, and the Word
was with God, and the Word was God. 1 He
was in the beginning with God; 2 all
things were made through him, and without him was
not anything made that was made.3 In
him was life, and the life was the light of men. 4 (John
1: 1-4 RSV-CE)
So looking again at Genesis 1, we see the Word being
spoken and creating. This Word, John tells
us, is both with God and therefore distinct from
God, yet, at the same time, the Word was God.
Genesis 1 mentions the Spirit moving over creation
and later, in Genesis 2:7, we read that God breathed
His very breath of life into Man. Again, in John,
we read "In
Him (the Word) was Life".
So the allusions to the Trinity are many, but
word Trinity is not found in the Bible. The formal
definition of the Trinity occurred at the Council
of Nicea in 325 AD. This was the first General Council
of the entire Church.
The teaching that God was Father, Son, and Holy
Spirit, had been handed down from the Apostles and
was rooted in Sacred Scripture. Exactly
how it should be comprehended in the human mind
had not been defined. In the early 4th Century, a
heretic by the name of Arius, began to teach that
the Son was not equal to the Father and that Jesus,
although a "god",
was not God Himself but a created being. In response,
the Church gathered in Council to formally address
the question and Trinity was defined.
Take care, be safe and tell your fellow soldiers
that you and they are in our prayers.