  We extend the approach of Banks, Myerson, and Kogut for the calculation of
the Wilson loop in lattice U(1) to the non-abelian SU(2) group. The original
degrees of freedom of the theory are integrated out, new degrees of freedom are
introduced in several steps. The centre group $Z_2$ enters automatically
through the appearance of a field strength tensor $f_{\mu \nu}$, which takes on
the values 0 or 1 only. It obeys a linear field equation with the loop current
as source. This equation implies that $f_{\mu \nu}$ is non vanishing on a
two-dimensional surface bounded by the loop, and possibly on closed surfaces.
The two-dimensional surfaces have a natural interpretation as strings moving in
euclidean time. In four dimensions we recover the dual Abrikosov string of a
type II superconductor, i.e. an electric string encircled by a magnetic
current. In contrast to other types of monopoles found in the literature, the
monopoles and the associated magnetic currents are present in every
configuration. With some plausible, though not generally conclusive, arguments
we are directly led to the area law for large loops.
