Seems clear enough to me. It's a short story: In the first verse, the singer is drunk and meets an aged soldier trying to drink away his memories of horror.

One summer evening drunk to hell
I sat there nearly lifeless
An old man in the corner sang
Where the water lilies grow
And on the jukebox Johnny sang
About a thing called love
And it's how are you kid and what's your name
And how would you bloody know

(He's sitting there drunk as a skunk, an old man in the corner is singing the song Where the Waterlilies Grow while on the jukebox, Johnny Cash is singing his song A Thing Called Love.

Next two verses are the old man incoherently telling the young fellow about his war experiences, in which, as he lay catastrophically injured and surrounded by the body parts of his comrades, he clings to the image of his sweetheart at home. But when he does get back (he and his comrades each wearing a label so the military hospital can identify them if they're incoherent), his lover has abandoned him.


In blood and death 'neath a screaming sky
I lay down on the ground
And the arms and legs of other men
Were scattered all around
Some cursed, some prayed, some prayed then cursed
Then prayed then bled some more

And the only thing that I could see
Was a pair of brown eyes that was looking at me
But when we got back, labelled parts one to three
There was no pair of brown eyes waiting for me

Brief break then for a chorus taken from traditional Irish and English music:

And a rovin' a rovin' a rovin' I'll go
For a pair of brown eyes

Back to the pub, where the singer and the war hero are looking at each other; the singer hates him because he wants to cling to the sickly-sweet images of popular country music - Philomena Begley and Ray Lynam's My Elusive Dreams, and to think about his own brown-eyed girl:

I looked at him he looked at me
All I could do was hate him
While Ray and Philomena sang
Of my elusive dreams
I saw the streams, the rolling hills
Where his brown eyes were waiting
And I thought about a pair of brown eyes
That waited once for me


Finally, an anodyne round-up to damp down the emotion of the previous images, followed by a repeat of the chorus:

So drunk to hell I left the place
Sometimes crawling sometimes walking
A hungry sound came across the breeze
So I gave the walls a talking
And I heard the sounds of long ago
From the old canal
And the birds were whistling in the trees
Where the wind was gently laughing

So a rovin' a rovin' a rovin' I'll go
For a pair of brown eyes
For a pair of brown eyes