The lyrics were written by Randall Wallace, the director and screenwriter for "We Were Soldiers" (he was also the screenwriter for "Braveheart" and "Pearl Harbor"). The music was written as part of the soundtrack for WWS by Nick Glennie-Smith.
It's wonderful to hear it on the WWS soundtrack, but I must say, if you want the full impact, rent WWS (warning: it's a graphic war movie along the lines of "Saving Private Ryan" - not for the young). As one not normally given to crying at movies, the scene where Mel Gibson's character returns home from Viet Nam got me going, and "Mansions of the Lord" over the end titles REALLY moved me.
A beautiful, majestic tribute to the fallen soldier who now lives in the presence of the Lord God Almighty.
The applause as the plane left the tarmac was very touching.
There's a poster on here called Aloha Ronnie who I believe was a member of that army company. He's a great guy.