Let $G=p^{n+m}.Q$ be an extension group of the special $p$-group $p^{n+m}$ by a group $Q$. Now $p^{n+m}=p^n{{}^\cdot}p^m$. How does one show that $\frac{G}{p^n}\cong p^m.Q$? Or equivalently that $G \cong p^n{{}^\cdot}(p^m{.}Q)$ (non-split extension of $p^n$ by $p^m{.}Q$?