that is the correct place for now, but the issue is going to be using the template. what you have now is:
{{War of 1812 |Pvt Capt DeBlanc's Co Louisiana Militia}}
which adds him to [[Category: War of 1812]] and displays and image with the text Pvt Capt DeBlanc's Co Louisiana Militia
{{War of 1812 | Louisiana}} will add him to [[Category: War of 1812, Louisiana]] but will lose the text Pvt Capt DeBlanc's Co Louisiana Militia
you should not do both templates as that would add him to both the general War of 1812 and War of 1812, Louisiana categories, we are only supposed to add people to the most specific category in the chain.
you could add him to {{War of 1812 | Louisiana}}, that will keep the icon, the correct category, and then list the rank/unit in the Militia Service section as a discrete item instead of buried in the reference line
we are still working on a document with all of the proposed standard military and war categories, once done it will get staffed to other project memners for concurrence, then off to the categorization project team for approval. once that is done, we will be able to start creating categories again and one can be made for William's Capt DeBlanc's Co Louisiana Militia and he would be moved into that by changing the template value