Casus Belli, in Latin, means a "cause of, or justification for, war." While not expressly programmatic, this piece is nevertheless meant to evoke and suggest powerful feelings and emotions to the listener. It was commissioned in 1986 by the Cedar Rapids, Iowa Metropolitan Orchestra Festival.

Structured in a rough sonata form, the main thematic ideas in Casus Belli are presented immediately. The forceful opening theme develops through rhythmic manipulations of a three-tone motive (diminished fifth, fourth, root) and around the pitches found in the Locrian mode.

The band version was created in 1993, but not premiered until February 3, 2024, by the Maine District 2 Honors Band.