In the paper *Homotopy properties of the poset of nontrivial $p$-subgroups of a group, Adv. in Math., 28(1978)*, D.Quillen proves a nontrivial version of Vietoris-Begle theorem. Recall that two a poset $P$ we can associate a simplicial complex, its *nerve* $|P|$. Any simplicial complex is, canonically, the nerve of a poset, the poset of faces. If $P, Q$ are posets, and $f: P\to Q$ is a monotone nondecreasing map, then its fibers are defined to be the subsets $$ f^{-1}(\leq y):=\bigl\{p \in P;\;\;f(p)\leq y\;\bigr\},\;\;y\in Q. $$ In the paper mentioned above Quillen proves that if $f: P\to Q$ is monotone nondecreasing and the fibers are homotopically trivial (resp. acyclic) then $f$ induces a homotopy equivalence between the nerves (resp. an isomorphism between the homology of the nerves). For more details see this [nice survey of Anders Bjorner.][1] [1]: https://people.kth.se/~bjorner/files/TopMeth.pdf