  We consider a 4d non-linear sigma model on the coset $(\mathrm{SU}(N)_L
\times \mathrm{SU}(N)_R \times \mathrm{SU}(2))/(\mathrm{SU}(N)_{L+R}\times
\mathrm{U}(1))\cong \mathrm{SU}(N) \times S^2$, that features a topological
Wess-Zumino-Witten (WZW) term whose curvature is
$\frac{n}{24\pi^2}\mathrm{Tr}(g^{-1}dg)^3 \wedge \mathrm{Vol}_{S^2}$ where $g$
is the $\mathrm{SU}(N)$ pion field. This WZW term, unlike its familiar cousin
in QCD, does not match any chiral anomaly, so its microscopic origin is not
obviously QCD-like. We find that generalised symmetries provide a key to
unlocking a UV completion. The $S^2$ winding number bestows the theory with a
1-form symmetry, and the WZW term intertwines this with the $\mathrm{SU}(N)^2$
flavour symmetry into a 2-group global symmetry. Like a 't Hooft anomaly, the
2-group symmetry should match between UV and IR, precluding QCD-like
completions that otherwise give the right pion manifold. We instead construct a
weakly-coupled UV completion that matches the 2-group symmetry, in which an
abelian gauge field connects the QCD baryon number current to the winding
number current of a $\mathbb{C}P^1$ model, and explicitly show how the mixed
WZW term arises upon flowing to the IR. The coefficient is fixed to be the
number of QCD colours and, strikingly, this matching must be 'tree-level exact'
to satisfy a quantization condition. We discuss generalisations, and elucidate
the more intricate generalised symmetry structure that arises upon gauging an
anomaly-free subgroup of $\mathrm{SU}(N)_{L+R}$. This WZW term may even play a
phenomenological role as a portal to a dark sector, that determines the relic
abundance of dark matter.
