  In recent work, we derived the long-distance confining dynamics of certain
QCD-like gauge theories formulated on small $S^1 \times \R^3$ based on
symmetries, an index theorem, and Abelian duality. Here, we give the
microscopic derivation. The solution reveals a new mechanism of confinement in
QCD(adj) in the regime where we have control over both perturbative and
nonperturbative aspects. In particular, consider SU(2) QCD(adj) theory with $1
\leq n_f \leq 4$ Majorana fermions, a theory which undergoes gauge symmetry
breaking at small $S^1$. If the magnetic charge of the BPS monopole is
normalized to unity, we show that confinement occurs due to condensation of
objects with magnetic charge 2, not 1. Because of index theorems, we know that
such an object cannot be a two identical monopole configuration. Its net
topological charge must vanish, and hence it must be topologically
indistinguishable from the perturbative vacuum. We construct such non-self-dual
topological excitations, the magnetically charged, topologically null molecules
of a BPS monopole and ${\bar{\rm KK}}$ antimonopole, which we refer to as
magnetic bions. An immediate puzzle with this proposal is the apparent Coulomb
repulsion between the BPS-${\bar{\rm KK}}$ pair. An attraction which overcomes
the Coulomb repulsion between the two is induced by $2n_f$-fermion exchange.
Bion condensation is also the mechanism of confinement in $\N=1$ SYM on the
same four-manifold. The SU(N) generalization hints a possible hidden
integrability behind nonsupersymmetric QCD of affine Toda type, and allows us
to analytically compute the mass gap in the gauge sector. We currently do not
know the extension to $\R^4$.
