Sure! We have a specific place for doing it, though: Community Promotion Ads.
Post an image advertising the proposal as an answer to Community Promotion Ads - 2017. If it gets six upvotes or more, your ad will then be shown periodically on the right sidebar, where people can click through to get to the proposal. This system lets the community vet what they do and don't want to promote, while still giving the ad plenty of promotion.
There are a couple of requirements your answer needs to follow, but they're detailed in the linked question. Be especially careful about size and formatting. There are some examples of promoting Area 51 proposals in the linked thread, as well as from 2016.
Finally, do try to make sure that the proposal is in some way relevant to the site. I'm not sure how much attention Militaria will garner on Worldbuilding Stack Exchange. It's worth a shot though; please do try it.