Being a 20 yr vet I understand the military, though not this one exactly.
I have trouble finding the metre/rhythm of this write as I read it so it becomes choppy.
You change the person you are writing in, which should be a constant.
Your use of "rapport" I think is incorrect as it is a noun.
stanza 8 line 1 "to" should be "too".
I had trouble finding either "enlaiden" or undenying in any dictionary I have at my disposal to include the on-line version.
As always an opinion.

At eighteen years of age,
Contemplating the possibilities.
Warfare in Iraq, should I engage,
Even though all the hostilities?
^^ great wording here the vocabulary is complex and that was refreshing. It was a good start to the poem

A young man in the making,
Fighting undenying fears
To leave his home, a practical undertaking,
While patriotism is the thought that will sear.
^^i know so many people who have family in the army and i know some guys in it...they are so brave for undertaking that burden you do a great job so far of portraying the entangled thoughts of a warrior

Military offices await ahead.
Slowly striding down the road,
Wearing white, blue and red
While whistling our national ode.
^^ the courage. I like the understatement here. They are in danger yet just casually whistling the national anthem! great portrayal here it caught my attention !

To defend our national homeland,
Where with our brethren he will part,
To warfare on the great white sands
As patriot, his destiny he will chart.
^^ this was a bit choppy but in a good way i liked it you made it work. the point got across and very well if i might add : )

Basic training now in store,
And soon flying to harms way.
Fellow soldiers must rapport,
United as one we'll never betray.
^^ i liked the last line ! so touching....honestly how such a young soul matures when in the army is amazing...

A Soldier signs a sinful pact.
Enlaiden with future remiss
His innocent heart to soon be cracked.
The love of his other he lacks.
^^a sinful pact....very artistic description that was my favorite part so far!

15th Infantry Regiment, 3rd Battalion
Camouflaged in hiding behind enemy lines.
Shots flying past, as I run like a wild stallion
Watching out for those dirty hidden mines.
^^ taking the reader into the heart of action!!! intense! I think you did a phenomenal job with that!

His boots worn from to many miles
Memories of home already burning through his mind,
So many laughs and smiles.
His heart and family across Atlantic bind.
^^ the first line i think it should be " too many miles" wow that must be tormenting to think about your family but not be able to hug them..again the courage it takes

Seeking shelter under fire,
Penetrating echos of fallen shells.
A distant home we'll soon acquire
Six insurgents, should we repel?
^^ it should be "echoes" ! but other than that great ending!!!

intense poem! i think the wording and flow were right on ! great job : ) 5/5

Thank you for doing this collab with me, I really enjoyed writting this first part of the series we are doing. Excellent work, you are very talented.

Peace, Joe

Well i have served the army for 2 years and i must say that you guys really know your stuff.The words and description really enables me to picture what the protagonist have to go through at such a very young age.

btw i think the 3rd stanza the 1st line u meant to say officers instead of offices?

I think this was an excellent collab the both of you really think the poem through as one mind.I am really unable to detect who wrote what.Excellent job guys would be looking forward to reading your part 2

Excellent Job
5/5 from me

"At eighteen years of age,
Contemplating the possibilities.
Warfare in Iraq, should I engage,
Even though all the hostilities?"

^^ I adore theswe opening lines, thought provoking and moving and pulls me right into the piece.

"A young man in the making,
Fighting undenying fears
To leave his home, a practical undertaking,
While patriotism is the thought that will sear."

^^I'm not to sure on this stanza..the piece starts of incredibly strong and this stanza seems to become a little weaker than what I was expecting.

"Military officers await ahead.
Slowly striding down the road,
Wearing white, blue and red
While whistling our national ode.

To defend our national homeland,
Where with our brethren he will part,
To warfare on the great white sands
As patriot, his destiny he will chart."

^^favourite stanzas so far. The flow here is flawless, words just roll right of the tongue, imagery is beautifully painted creating such vivid pictures in my mind and the emotion and depth is overwhelming.

"Basic training now in store,
And soon flying to harms way.
Fellow soldiers must rapport,
United as one we'll never betray.

A Soldier signs a sinful pact.
Enlaiden with future remiss
His innocent heart to soon be cracked.
The love of his other he lacks."

^^ This is more like it =) I'm finding this piece to become stronger and stronger throughout now, and the emotion here pulls on the heartstrings, and I can't wait to continue on.

"15th Infantry Regiment, 3rd Battalion
Camouflaged in hiding behind enemy lines.
Shots flying past, as I run like a wild stallion
Watching out for those dirty hidden mines.

His boots worn from too many miles
Memories of home burning through his mind,
So many laughs and smiles.
His heart and family across Atlantic bind."

^^ Ohhhh, these stanzas brought tears to my eyes..the depth here is incredible and as I'm halfway through the entry requirements for the army myself, this creates such conflicting emotions for me.

"Seeking shelter under fire,
Penetrating echos of fallen shells.
A distant home we'll soon acquire
Six insurgents, should we repel? "

^^Love this closing, I liked how you left it open for the reader to take any way they wanted, and found this to be a beautiful way to wrap up this piece.

You can always tell when a collab is good when you can't tell who wrote what as is the case here, and once I get some more free time, I'll certainly be reading the other installments of this.

Beautiful work!