Yes, I think the movie would have done much better if it had been promoted at all... it was truly a victim of the demise of Miramax. However, war movies in general don't do very well. Even movies perceived of as hits like "Once We Were Soldiers" lost money.
BTW, the lack of any successful foreign-language movie is noteworthy. The wire-fu slapstick, "Kung Fu Hustle" was the closest thing to an American success. This is quite an interesting development, after years of successes such as "Crouching Tiger, Hidden Dragon," "Life is Beautiful," "Amelie," "The Passion of the Christ," "City of God, "Hero," and "Monsoon Wedding."
The top foreign-language films of 2005 (besides Kung Fu Hustle), listed by their rank among all-time foreign language films:
39. Downfall (German)
63. High Tension
64. The Chorus
79. Walk On Water
116. Look at Me
Compare this to last year:
1. The Passion of the Christ
4. Hero
10. The Motorcycle Diaries
17. House of Flying Daggers
29. Maria Full of Grace
(Unless you consider Wallace and Gromit to be a foreign-language film :^D)