"Harch" is the command issued by the Drum Major

Drum Major

A drum major is the leader of a marching band, drum and bugle corps, or pipe band, usually positioned at the head of the band or corps. The drum major, who is often dressed in more ornate clothing than the rest of the band or corps, is responsible for providing commands to the ensemble regarding...

 of a marching band

Marching band

Marching band is a physical activity in which a group of instrumental musicians generally perform outdoors and incorporate some type of marching with their musical performance. Instrumentation typically includes brass, woodwinds, and percussion instruments...

, or by a Sergeant in charge of assembled troops, to move forwards upon the left foot. The command most commonly issued is "For'd, Harch" meaning for the entire group to move forwards as one body. "For'd" is the attention-getting and directive part of the command; "Harch" is the executive part of the command.

The term "harch", rather than "march" is used, as the latter term may easily be scattered by noise

Noise

In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...

. For similar reasons, the contraction "for'd" is (preferably) used rather than "forward." Also, the term march may be confused with a number of other commands that include this word

Word

In language, a word is the smallest free form that may be uttered in isolation with semantic or pragmatic content . This contrasts with a morpheme, which is the smallest unit of meaning but will not necessarily stand on its own...

, e.g., "To the Right Flank, Harch."