  We consider a Yang--Mills theory in loop space whose gauge group is a
Kac--Moody group with the central extension. From this theory, we derive a
local field theory constructed of Yang--Mills fields and abelian antisymmetric
and symmetric tensor fields of the second rank. The Chapline--Manton coupling,
that is, coupling of Yang--Mills fields and a second-rank antisymmetric tensor
field via the Chern--Simons 3-form is obtained in a systematic manner.
