As such characters will gain training into certain fields, they will improve their skills from the basic levels to the more advanced. Ribbons and MOS specialization will represent this and will enable this. Certain ribbons and all medals will represent achievements, others will open new skills and levels.
A certain amount of ribbons and medals will be required to attain higher level training and eventually obtain special forces status : Ranger, Delta, SEAL, sniper, etc. (or equivalent in other countries armed forces). Eventually granting what players want, total badassness!
A character's achievements and medals can be converted to unit points upon the character's demise (death, incapacitation through injury, or becoming MIA). These points are "player experience points" which allows the player to pay for a higher ranking new character and not start from zero. This allows the player to build a unit of highly qualified characters, thus the term "unit points".
Unit points are meant to address two elements: lethality and heroism. Characters will die and that's a fact of war, sorry no rules pampering in the game. Unit points mitigate some of the issues around a highly lethal game, the player doesn't lose everything when the character dies. They can pick up with a new character and not have to start from zero.
The other aspect, which I find even more important, is heroism. Granting the PCs posthumous medals are a way to retribute the player for excellent play. Imagine, the PC dies and the player is granted the Medal of Honor posthumously. Not only a great ending for a dear character, but also the great beginning of a new story.