  It was pointed out by Shifman and Yung that the critical superstring on
$X^{10}={\mathbb R}^4\times Y^6$, where $Y^6$ is the resolved conifold, appears
as an effective theory for a U(2) Yang-Mills-Higgs system with four fundamental
Higgs scalars defined on $\Sigma_2\times{\mathbb R}^2$, where $\Sigma_2$ is a
two-dimensional Lorentzian manifold. Their Yang-Mills model supports semilocal
vortices on ${\mathbb R}^2\subset\Sigma_2\times{\mathbb R}^2$ with a moduli
space $X^{10}$. When the moduli of slowly moving thin vortices depend on the
coordinates of $\Sigma_2$, the vortex strings can be identified with critical
fundamental strings. We show that similar results can be obtained for the
low-energy limit of pure Yang-Mills theory on $\Sigma_2\times T^2_p$, where
$T^2_p$ is a two-dimensional torus with a puncture $p$. The solitonic vortices
of Shifman and Yung then get replaced by flat connections. Various
ten-dimensional superstring target spaces can be obtained as moduli spaces of
flat connections on $T^2_p$, depending on the choice of the gauge group. The
full Green-Schwarz sigma model requires extending the gauge group to a
supergroup and augmenting the action with a topological term.
