  Non-perturbative contributions of the Euclidean path integral are important
to understand the information loss paradox. In this paper, we revisit the
Yang-Mills instantons in the Einstein-Yang-Mills theory. There exists a
globally regular solution that is known as the Bartnik-McKinnon solution and a
black hole solution. The regular and the black hole solutions are smoothly
connected in the small horizon limit. Their Euclidean action is solely
characterized by the ADM mass, and the transition probability follows the usual
Bekenstein-Hawking entropy formula. Therefore, the Yang-Mills instantons
provide a non-perturbative channel to the black hole evaporation, which
competes effectively with perturbative processes, and becomes dominant toward
the end of evaporation. We show that these instantons provide a smooth
transition mechanism from a black hole to regular spacetime.
