  We prove a generalization of the classical Klein-Maskit combination theorem,
in the free product case, in the setting of Anosov subgroups. Namely, if
$\Gamma_A$ and $\Gamma_B$ are Anosov subgroups of a semisimple Lie group $G$ of
noncompact type, then under suitable topological assumptions, the group
generated by $\Gamma_A$ and $\Gamma_B$ in $G$ is again Anosov, and is naturally
isomorphic to the free product $\Gamma_A*\Gamma_B$. Such a generalization was
conjectured in our previous article with Bernhard Leeb (arXiv:1805.07374).
