It is excruciatingly difficult to try and find good sources on the Forest Brothers and other fascist organizations in English. This is mostly because many Baltic governments, and even NATO themselves have long since whitewashed Nazi collaborates in the Baltics as “Glorious Anti-Communist Freedom Fighters”.

The best I’ve been able to find is this decent by a writeup by this British organization, which while western, at least accurately displays the crimes and affiliations of various Lithuanian Groups. https://hopenothate.org.uk/2018/01/02/nato-forest-brothers-movie-madness-worst/

What also will make researching various fascist groups in the Baltics difficult is that many groups reorganized many times, and changed names frequently, despite changing nothing about themselves and having more or less the same leadership. For example, the Forest Brothers were also known as the Lithuanian Activist Front, Lithuanian Liberation Army, Arajs Kommando, and Union of Lithuanian Freedom Fighters, among many many many other names and fronts.

As for a source on Germans turning on their pawns, this is the story of SS Obergruppenführer Friedrich Jeckeln. Jeckeln was a deranged evil man, that even other Nazis pale in comparison too, as he was the operational commander of all Einsatzgruppen Mobile Death Squads stationed on the Eastern Front, and was personally responsible for ordering and participating in the murder of over half a million Jews, Slavs, Romani, handicapped, and other undesirable groups. He was so talented in mass murder, that he not only invented the process of “Sardine Packing” to maximize the amount of people that could be fit into mass graves, he also created an entire working system to execute as many people as possible in the shortest possible time, with the smallest amount of resources (The Jeckeln System). He also personally loved ordering and taking part in mass executions, viewing the occasions as parties where he could relax with his friends.

Where the Forest Brothers fit into this is that they were one of Jeckeln’s favorite Einsatzgruppen operative groups. While in German service the Brothers were known as Arajs Kommandos, and this group accompanied Jeckeln on almost all of his mass killing sprees in the Baltics, with most famously taking part in orchestrating the Rumbula Massacre where Jeckeln would personally receive a War Merit Cross from Hitler for his actions. In this massacre 1,700 Lithuanian Kommandos forced 25,000 Jews from the Rumbala Ghetto out into a nearby field in the middle of the night. They then proceeded to tie people together in pairs, before shooting one person of the pair and dropping both into the mass grave so that the other person would be crushed to death in order to save bullets. This went on for two days straight, with only 3 survivors escaping out of the original 25,000. It was so brutal and inhumane, that a reporter there to collect a field detail for Himmler reported that, quote, “some of the experienced SS Einsatzgruppen killers were horrified by the savagry and cruelty displayed by the local collaborators”.

This can be found even on his Wikipedia page, but after the war, Jeckeln was captured by Soviet forces and sentenced to death. During the few months he had left before his execution in 1946, he divulged all of the information he had on the Brothers to the NKVD, and handed over maps, documents, and operations logs that led to the capture of many Forest Brother cells. He apparently did this out of guilt for his actions… as if that would save him from whatever hell his soul is burning in…

Unfortunately I don’t have a source for ‘SS officer attachés […] were so disgusted with the actions of Baltic Nazi Partisans that many decided to volunteer in assisting Red Army forces in capturing and stopping the partisans after the war’, but for now, I can tell you this:

According to Mindaugas Pocius, a Lithuanian historian and author of “The Far Side of the Moon” (Kita mėnulio pusė), an extensive study on the reprisals, over 9,000 civilians — including no fewer than 300 children — were designated as collaborators, court‐martialled and executed by the Forest Brothers.

(Source.)

You know how in some friend groups there is the one person that stands out like a sore thumb? Like a kid from a lower class family in a friend group of very wealthy kids? And how that person sometimes over compensates to an extreme degree, due to their insecurity, so that the others will like them? That’s what many SS collaborators were like, along with the fact that many of them were just as absolutely deranged as their masters.

The few “true idealists” among their ranks, the German general continues, “who combined a pronounced anti‐Bolshevik attitude with a fanatical love for their own people” were among the most brutal and violent of all the [Axis’s] legions when it came to dealing with the civilian population in the [Axis]‐occupied regions, precisely because they were generally regarded as traitors by their own people. “They were extremely harsh toward fellow countrymen who failed to share their ideals,” Heygendorff writes. “In dealing with undependable individuals they were so severe that we frequently had to intervene” (emphasis added)—a German euphemism that indicates that the “idealists” were often responsible for mass murders of innocent civilians during the antipartisan campaigns.

(Emphasis added. Source.)

The most village-y part of the world that is inside Anglosphere. The worst elements will come from there and from “the woods” type of people from USA.