  We present a proof of the Britto-Cachazo-Feng-Witten tree-level recursion
relation for gluon amplitudes in QCD, based on a direct equivalence between
BCFW decompositions and Feynman diagrams. We demonstrate that this equivalence
can be made explicit when working in a convenient gauge. We exhibit that gauge
invariance and the particular structure of Yang-Mills vertices guarantees the
validity of the BCFW construction.
