That's a generous interpretation of the word most. Among active duty plus veterans the US military is 34% Republican. If you take out veterans it's only 26%.

https://news.gallup.com/poll/118684/military-veterans-ages-tend-republican.aspx

and red states are the only ones with some semblance of a manufacturing base

Straight up ridiculous nonsense.

https://www.industryselect.com/blog/top-10-us-states-for-manufacturing

California is not only top for manufacturing, but grows half the food in the country.

I dont think a hypothetical civil war will turn out as well as blue staters think.

It's not going to happen, not even in your wildest, most traitorous fever dreams.