Spirit of Fire is the first track in the Halo Wars Original Soundtrack. It is one of the first songs the player will hear, as it plays at the game's opening menu. It is also featured in the end of Homecoming. It runs for a total of 2 minutes and 4 seconds.
It starts with a very moody piano solo - a rendition of the Spirit of Fire's Theme, with atmospheric electronic backing, with drums, strings, bells and a choir joining at 0:27. After the first 'climax', the piece segués into a new arrangement of the Halo Theme, with added piano, drum and electronic elements, and a new arrangement for the famous Gregorian chant element. This reaches a crescendo at 1:48, after which the piece ends with a continuation of the background instruments and sounds, which slowly fade out.
The track sounds very similar to the "Five Long Years" track found only on the DVD exclusive tracks, but the two are not the same. The Spirit of Fire's motif as heard at the beginning of the song is repeated several times throughout the Halo Wars soundtrack, particularly in cut scene events focusing on the ship itself, such as "Freaked Out" and "Insignificantia".