Complex sentence: The SS rank of Unterscharführer was created after the Night of the Long Knives which caused a reorganization of the SS and the creation of several new ranks to separate the SS from the "Sturmabteilung" (SA).
Split into simpler sentences: The SS rank was created after the Night of the Long Knives. That event caused an SS reorganization and the creation of new ranks to separate the SS from the "Sturmabteilung" (SA).