The 13th Struggle

"The 13th Struggle" is a musical theme composed by Yoko Shimomura that appears in Kingdom Hearts Chain of Memories, Kingdom Hearts II, and Kingdom Hearts III.

Appearances
"The 13th Struggle" is a theme commonly used during boss battles with members of Organization XIII.

Sora's Story

 * Boss battles: Axel, Larxene, and Vexen

Reverse/Rebirth Mode

 * Boss battles: Vexen, Lexaeus, Zexion.

Kingdom Hearts II
"The 13th Struggle" plays during both boss battles and cutscenes. It can also be heard during certain events, such as when the trio teams up with Axel to defeat the Nobodies in Betwixt and Between.

Cutscenes

 * Prologue: Axel, Axel's Wrath
 * Twilight Town (Third Visit): Axel's Atonement, The Words I Wanted to Say
 * The Land of Dragons (Second Visit): The Man Who Stands on the Snowy Mountain
 * The World that Never Was: Luxord, As the Battle Ends

Boss Battles

 * Twilight Town: Axel (Roxas); Axel's Replica Data (Sora)
 * The Land of Dragons: The Mysterious Man
 * The World That Never Was: Luxord and his replica data

Kingdom Hearts coded

 * Castle Oblivion: ???.

Kingdom Hearts III

 * Keyblade Graveyard: Luxord

Kingdom Hearts III Re Mind

 * Garden of Assemblage: Luxord's Recreated Data, Larxene's Recreated Data

Composition
"The 13th Struggle" is approximately two minutes and twenty-nine seconds long and one minute and forty-four seconds long. In all versions the tempo is 178 beats per minute. It has a time signature of 4/4 time for the entire piece. "The 13th Struggle" has a four measure introduction that leads into the repeated melodic section, and lacks a conclusion, allowing for smooth transitions between loops. Each loops is forty minutes long, lasting around one minute each. The instrumentation consists of: organ, a large brass section featuring trombones, choir, strings, orchestra bells, snare drum, piano, cymbals, and timpani.