Let $R$ be a Henselian, local ring with maximal ideal $\mathfrak{m}$. Let $M$ be a finitely generated $R$-module, that is indecomposable.
It can be shown, that in this case the Endomorphism ring $End_R(M)$ is a local ring.
So let $h\in End_R(M)$. Assume that $h$ is not a isomorphism. Than $h$ is not a unit and hence lies in the maximal ideal of $End_R(M)$ which is the same as the Jacobson radical.
Why can I conclude that some power of $h$ is in $\mathfrak{m}End_R(M)$?