Halo Wars multiplayer ranks
From Halopedia, the Halo wiki
For calculating matchmaking player matchups, Halo Wars employs Microsoft's TrueSkill technology. This is used to match players into games, with each player assigned a different rank for each playlist in the game. If a player searches as part of a party, the average TrueSkill rank for the party as a whole is used. TrueSkill ranks were used on the Halo Wars leaderboards.
In addition to TrueSkill, Halo Wars calculated a 1-50 numeric skill rank for each player based on how they performed in each game they played. The skill ranks are not used in matchmaking, and are only calculated for bragging rights. Skill ranks were not viewable in-game, but could instead be viewed on halowars.com, prior to its shutdown.
Score ranks are the main ranks a player sees in game, represented by a UNSC military rank and a unique icon (the same as the ranks featured in Halo 3). Score ranks were implemented to help visually represent a player's experience in playing Halo Wars, and represent a total tally of all the score earned by the player in every multiplayer game they have played. The Service Record shows the player's current rank, score and how many more points the player needs to rank up. The player's rank is also visible as an icon next to their gamertag when in a game lobby, post game screen and other areas. There are eight ranks available in Halo Wars. The player starts as Unranked, and then is promoted to Recruit upon completing their first public Matchmaking game.
As a match progresses, players earn a "Base Score" for which they earn points by killing enemy units and buildings; Base Score is maxed out at 4000 points. At the end of the match the base score is multiplied by the "Bonus Score," resulting in a "Total Score." Bonus score is calculated based upon several factors. To earn the bonus, the player must complete a Public Matchmaking game and not disconnect. If the player wins, they receive an additional 40%. If the player loses, they still get an additional 20%. If the player is out of the game early and wants to leave, they will still receive the 20% bonus. Bonus score is also affected by "Combat Efficiency", a rating of 1-5 which is based on the number of units and buildings killed in relation to the number of units and buildings lost. The maximum Bonus Score is 8.40X, making the maximum "Total Score" for a single match 33600 points.
The Running The Show achievement can be unlocked by hitting the rank of General in Halo Wars.
Halo Wars: Definitive Edition ranks
Ranks in Halo Wars: Definitive Edition work the same way as in the original game, with the same ranks and requirements as listed above. However, in addition to the original eight ranks found in the original game, Halo Wars: Definitive Edition also introduced three new ranks after General; Three-, Four- and Five-Star General, respectively. Their current unlock requirements as presently unknown. This brings the total number of available multiplayer ranks to eleven.
Rank score requirements
When Halo Wars launched, the rank XP requirements were considerably higher and harder to achieve than later iterations. Throughout the Halo Wars Title Updates #2 and #4, the rank requirements were decreased twice due to a wish to make earning the Running The Show achievement easier for newer players. The older score requirements are listed in the below table. The values seen in the Title Update 4 column represent those seen in the current builds of Halo Wars and Halo Wars: Definitive Edition