The 15th Waffen-Grenadier Division der SS was based on the Latvian internal security units - i.e. "Schuma Battalions." In early 1943, the "Lettische SS-Freiwilligen Legion" was formed from a combination of several of these Schuma Battalions plus possibly elements of the 2nd SS Infantry Brigade (see Totenkopf Standarten)
The 15th SS crumbled under massive Soviet attacks in the beginning of July 1944. Reformed again in September, it was sent back into the Soviet meat grinder and again suffered from heavy losses and crumbling morale and by 1945 had pretty much desintegrated as a coherent fighting unit. Many of its better troopers were used as replacements for the superior 19th SS Divison.