Heyo Captains,
Firstly, for all of you who are Veterans of the various forces, we at Wargaming thank you for your service.
The Military Month Contributor flag was a final reward for a Charity Campaign benefitting Fischer House in May 2016, in which Wargaming Pledged to donate $1 per a mission completed up to $100,000 across Ships, Tanks and Planes. The full details of the event are documented here: https://worldofwarships.com/en/news/general-news/military-appreciation-month-2016/
As with anything in life, events come and go, if you were not there during them, it is unreasonable to expect to receive the rewards for that event simply on the premise that they relate to you. Rewards are not retroactive.
From the event, we did recognise that those with the flag no longer used other flags available to them, this was an impact we were not happy with, and thus discontinued this flag, and decided against adding other flags with economic bonuses. That is one thing to recall with this flag; it is only providing economic bonus, it does not offer game influencing multipliers to the ship equipped (such as higher fire chance etc). These multipliers are also extremely minimal in nature: +5% to be exact.
For the time being, this flag will not be reintroduced. In the future we may have similar events that benefit military based charity's (or charities in general), which will have other rewards / incentives available that will likely be restricted to that promotion which future players will not be able to obtain.
Keep an eye out around Military Branch's Birthday and other military based holidays for goodies to become available that can show your support and/or service for the Military if you are interested in representing this as you sail the seas.
Fem,