Base defences have been a part of RTS since its inception and are often regarded as being a simple yet necessary component of RTS games. In reality, designing base defences should be done with great caution because the flow and pacing will suffer if turtling is too effective. Regardless of the implementation, there are a few considerations to ensure base defences are a balanced and fun component of RTS.
So why should an RTS even bother with base defences in the first place? Like a lot of other mechanics, they aren’t always necessary and shouldn’t just be tacked on for the sake of it. If done properly, base defences act as a strategic tool which reward players for their foresight and predictions of enemy movements since they fortify certain locations of the map at the expense of mobility, resources or time. The most fundamental method to balance out base defences is for mobility to be incentivised through game mechanics such as resource acquisition and tied together with meticulous map design.
Secondly, it’s important for base defences to have vulnerabilities and weaknesses which can be exploited. Ideally, base defences would have just as much interaction and counter play as any other unit type. Various RTS handle this in different ways; Command and Conquer Zero Hour has base defences that are weak versus certain unit types such as Gattling Cannons being weak versus tanks while Patriots are weak versus infantry. Alternatively, Firebases are strong against all unit types but have a minimum attack range.
The Point Defence in Supreme Commander takes a different approach; they’re strong versus all ground units, but Mobile Artillery is readily available from the start and is a strong counter. In Company of Heroes, machine gun teams and anti-tank guns can only fire in a limited arc which allows them to be flanked. At first glance, StarCraft 2 appears to be an exception to this rule since its defences have no obvious weaknesses and siege units are inaccessible. Instead, StarCraft’s defences are weak for their size and attack range compared to units, so they scale poorly against large armies that can have more damage packed into a smaller area.
All of these unique approaches work because it allows for players remain active and aggressive since they always have the ability to punish the defensive structures, it also means base defences need to be supported and can’t just be placed down and neglected. These implementations are especially brilliant because each is thematic to the overall focus of their game, whereas flanking Point Defences in Supreme Commander would feel out of place for a game that’s focused on production and allocation of units.
So now that we know how to make base defences balanced, how do we make them fun? Depending on the focus of the game, base defences should have quirks and interaction to bring them to life and give them their own unique personality. Zero Hour does this excellently with micro techniques such as retargeting the EMP Patriot during its volley to disable multiple vehicles, or spinning up the Gattling Cannon before an engagement to increase its rate of fire. Even better is when these traits create room for both players to micro and outplay each other; the Patriots in Zero Hour don’t track moving infantry which allows a player to identify which infantry is being targeted and keep it moving to avoid damage. Meanwhile, the Patriot can retarget another infantryman or can manually attack ground to intercept the moving target. In Company of Heroes, heavy machine gun(HMG) teams can be smoked off which prevents it from firing, but it also gives the HMG team time to reposition.
Other than just micro techniques, base defences can have more strategic approaches to make them enjoyable, Red Alert 3 accomplishes this by allowing them to be customised or improved. For example, a Tesla Coil has its damage increased if charged by a Tesla Trooper, the Multigunner Turret can be garrisoned by different infantry to customise the weapon, and nearby Spectrum Towers can link up to each other. They’re elegant implementations because they create ways to improve the efficiency of base defences while requiring foresight and investment of resources. These characteristics are also all visually intuitive for the type of weapons they wield; it would be jarring to charge up a machine gun like a Tesla Coil, but it does make sense for a machine gun to load incendiary rounds.
Even outside of gameplay, base defences should be designed in a way that makes them satisfying to use. There’s nothing cool about machine guns and rocket launchers; the most memorable base defences in RTS have been the Tesla Coil and Obelisk of Light because of their attack type, sound effects and kill animations being something completely unique to Command and Conquer and Red Alert. In later Command and Conquer games, the Obelisk of Light was no longer special because of how many units fired lasers with similar visuals and audio. The Spine Crawler in StarCraft 2 is fantastic because it’s literally a giant spine which impales victims, which is far more awesome than the boring Spore Crawler which just shoots spores. If it’s appropriate, base defences should try to find exclusive weapon types and effects to make them stand out.
So far I’ve been talking about base defence as just static turrets, but that’s not always the best approach to defending territory, and many RTS have handled it more creatively. Company of Heroes has several features to make attacking and defending territory more strategic and complex, in which barbed wire and sandbags can be deployed to deny or create cover, HMG teams can be set up to suppress incoming troops in a limited arc, and mines can be used to slow an advance. Whatever the method of defence is, it’s important they each have an opportunity cost in resources or time to make them a deliberate decision which requires preparation, and just like static turrets, utility based defences should have counters such as wire cutters and mine sweepers.
Base defences can come in many different forms, but they all serve to fortify locations of the map at the expense of mobility, resources or time. They should serve a strategic purpose by requiring preparation and prediction of enemy movements. Base defences need to have vulnerabilities which can be exploited or have accessible counters to ensure they don’t stop the game from flowing. Additional quirks, micro techniques and unique artistic qualities should be used to create base defences as an enjoyable feature and not just as a generic RTS trope.