Birge's Western Sharpshooters need help on Colonel Birge, how did he get to be the first Colonel?

[csuniforms]

Hello, I am currently writing a book on Civil War combat, rifles vs. smoothbores and it did make a difference. Am working currently on Fort Donelson and the ordnance carried by both sides and the Veterans comments on what they were issued and how they faired in the actual fighting. A big part of the story of Fort Donelson is the contribution of Birge's Western Sharpshooters. I cannot find how and why Fremont picked Birges to command the Sharpshooters. He was a New York Militia Officer and given the rank of Mayor General in the Canadian Uprising in 1838. He was a Doctor with a degree, escaped from jail and ended up in St. Louis. He was later put under arrest and resigned from the Army in 1862. Any help appreciated.

Tom Arliskas
CSuniforms