This song is a FL studio cover of the epic song by viking metal band, Turisas, called "Rex Regi Rebellis". It took me about 2-3 months on and off to finish this because I kept putting off after finishing certain parts. Here's what Mathias "Warlord" Nygård of Turisas has to say for the song itself:

"I've been facinated by the Thirty Years War almost since I was a child - specially the Finnish cavlary, The Hakkapeliittas, who were feared among enemies and highly respected by fellow soldiers. Our first demo "Taiston Tie - The Battle Path" from 1998 was around the same theme, so this Thirty Years War -song has been a long project that has hanged with us since the day Turisas was founded.
The name for the song is taken from Topelius' Surgeon's Stories too. In the novel, the initials R.R.R. was engraved into the king's ring, which has a leading role throughout the story. Rex Regi Rebellis is Latin and could be translated into "the king is rebellious towards the king".
The English lyrics are my own and the Swedish ones are from another text by Topelius "Finska rytteriets marsch i trettiåra kriget" (The March of the Finnish Cavlary in the Thirty Years War)
Since Topelius was Finno-Swedish as myself, I wanted to use the original Swedish text. The pick also had to do with the fact that in the days of the Thirty Years War, Finland was a part of Sweden and so the Finnish soldiers and cavlary actually fought side by side with the Swedes."