Halo Wars 2 is a military science-fiction real-time strategy video game, in which players command armies from a bird’s-eye view of the battlefield. The game can be played using a gamepad or using a mouse and keyboard. Like its predecessor Halo Wars, the game features two playable factions: humanity’s main military arm, the United Nations Space Command (UNSC), who return from the first game, and a new alien faction known as the Banished, who serve as replacement for the Covenant. A story-based campaign mode lets players take control of UNSC forces in battles against the Banished on an ancient structure. The campaign consists of twelve missions that can be played alone or cooperatively. Each mission presents main objectives that involve capturing points, defending bases, or surviving waves of enemies, and often require the player to lead Spartan supersoldier units around the map. The campaign also features optional side objectives such as ensuring a certain unit survives over the course of a mission or destroying extra bases within a time limit. Animated cutscenes and dialogue precede each mission to provide context and integration with the game’s story.
Outside the campaign, both the UNSC and the Banished are playable; each faction has a distinct set of units. Players choose a leader that is based on a prominent character and emphasises a particular style of play. Leaders have unique abilities that can be upgraded and activated during a battle; using one triggers a cooldown period before it can activated again. Healing groups of units, carpet bombing a targeted area, and deploying special troops are examples of some leader abilities. Combat in Halo Wars 2 is balanced by a “rock–paper–scissors” counter-attack system, in which ground vehicles are effective in combat against infantry, infantry are effective against aircraft, and aircraft are effective against ground vehicles. In most game modes, the player establishes a base of operations at a predetermined location on the map. Barracks and vehicle depots can be constructed at a base to deploy infantry and vehicles for combat. Each unit deployment, building construction, and leader ability requires supplies, a resource that can be gathered on the battlefield or collected via a supply pad building. Some units and buildings also require a second resource—power, which is produced using a generator or extractor building. Base buildings can be upgraded to grant passive bonuses and unlock access to higher tier units. Initially, the battlefield is shrouded by a fog of war, which can be uncovered by moving units to clouded regions of the map. Units can be selected and then commanded to engage in combat or interact with structures on the battlefield. In addition to their primary attacks, every unit has a special ability and certain units have two abilities. For example, Spartans are capable of hijacking vehicles and performing a smash attack after leaping into the air. The player can build additional bases once they have accumulated enough resources and gained control over areas of the map, which allows them to expand their army further.
Halo Wars 2 features a number of multiplayer modes that can be played online with up to six players. Skirmish is a cooperative or solo play mode against AI opponents. Deathmatch involves eliminating the opponent’s army. Stronghold and Domination are territorial modes centered around controlling bases or nodes on the map. Blitz is a mode that combines elements from collectible card games with RTS gameplay by replacing the base building and resource management with a card-and-deck mechanic for unit deployment. Players create decks from card packs that are earned by playing the campaign mode and completing daily challenges. Each card features a unit that is deployed on the battlefield. Energy is the resource for using cards; more powerful units have a higher energy cost. Energy generates automatically throughout a match and more can be collected as additional energy supplies are dropped onto the map periodically. There is single-player and cooperative variant of Blitz named Firefight, which pits players against waves of AI enemies.