Adolf Hitler issues a decree at the behest of Heinrich Himmler that armed SS troops would play a role in both foreign and domestic affairs. This is the final step in the creation of the Waffen-SS, an armed, military wing of the SS that constitutes a rival to the regular army which military leaders had once feared the SA would become.
As of today, service in the Waffen-SS will fulfill any military obligations a person has.
The Waffen-SS got its start with the creation in 1934 of the the SS-Verfügungstruppe (SS Dispositional Troop, SS-VT), special armed SS troops under Hitler's direct, personal command. The SS-VT depended on the regular army for weapons and training, but they've been growing gradually more independent.
Members of the SS and the Waffen-SS must be Aryan, and while they can belong to any religion, atheists are absolutely banned. Heinrich Himmler wrote to a pastor in 1937:
"Atheism is the only world-view or religious view that is not tolerated within the SS."