  We study the $T^2$ compactification of a class of 6d $\mathcal{N}{=}(1,0)$
theories that is Higgsable to $\mathcal{N}{=}(2,0)$ theories. We show that the
resulting 4d $\mathcal{N}{=}2$ theory at the origin of the Coulomb branch and
the parameter space is generically given by two superconformal matter sectors
coupled by an infrared-free gauge multiplet and another conformal gauge
multiplet. Our analysis utilizes the 5d theories obtained by putting the same
class of 6d theories on $S^1$. Our class includes, among others, the 6d
theories describing multiple M5 branes on an ALE singularity, and we analyze
them in detail. The resulting 4d theory has manifestly both the
$\mathrm{SL}(2,\mathbb{Z})$ and the full flavor symmetry. We also discuss in
detail the special cases of 6d theories where the infrared-free gauge multiplet
is absent. In an appendix, we give a field-theoretical argument for an
F-theoretic constraint that forbids a particular 6d anomaly-free matter
content, as an application of our analysis.
