Engage the Enemy

Engage the Enemy is Disc 1, Track 9 on the Xenoblade Original Soundtrack. It plays during cutscenes before and after important boss fights in the game:
 * Metal Face attacking Fiora in Colony 9 (The music continues as the battle theme for the subsequent battle until the track ends.)
 * Before the battle against the in Spiral Valley
 * Before the battle against Xord in the Ether Mine
 * The cutscene between the two phases of the Leone Telethia (The music continues as the battle theme for the second phase until the track ends.)
 * Metal Face appearing on Prison Island
 * After the fight with Mumkhar on Valak Mountain
 * After the battle with Mumkhar in Sword Valley
 * The battle between Zanza and Meyneth in the Mechonis Core
 * Between the two phases of the battle against Dickson

As part of a promotional video for Xenoblade Chronicles 3D, this track was rearranged by Tomori Kudo.

Engage the Enemy (Definitive Edition)
Engage the Enemy is Track 3 on the Xenoblade Chronicles: Definitive Edition Sound Selection. It is a rerecording of the original with slightly altered balance, mixing, and orchestration (e.g. at 1:38, the vocal line follows the melody more closely than in the original).

In the base game, it plays in the same situations as the original. In Future Connected, it plays when the Telethia destabilise the Fog King's rift, allowing Melia to finish it off.

In Super Smash Bros.
A shortened and looped version of (the original version of) Engage the Enemy is one of the music tracks in both and, available on the  and (in Super Smash Bros. Ultimate) the  stages.

A section of the piece was also remixed for the Xenoblade Chronicles Medley.

In Project X Zone 2
A remix of Engage the Enemy was made for Project X Zone 2. It plays in Chapter 6, 'You Will Know Our Names', when Fiora introduces herself to KOS-MOS, as well as later on when Metal Face appears.

Trivia
There exists a post-battle dialogue in Xenoblade Chronicles 2 between Ursula and Rex during which they sing a tune that sound very similar to Engage the Enemy. There is also a similar dialogue with Electra.