RTS Basics

Unit Types

Regardless of how the game is built, most unit ensembles strive for a nice mix of everything: basic grunts, heavy slow powerhouses, fast, light scouts, a few specialists, workers and maybe a few spicy extras - covert spies, saboteurs or spellcasters that go beyond the normal move'n'shoot. Whatever they turn out to be, you'll find your RTS game is using units very similar to other RTS games. You know: tanks, infantry, cavalry, spies and boats, to name but a few. There's a set of conventions most regular RTS titles follow. For example, if a unit is small, its likely to be light and nimble; if its big, then its slow, ponderous, expensive but powerful; a physically powerful unit will be susceptible to magic; a magic unit will fall prey to the weakest physical unit in the field; scouts are light and fast; defender units tend to have better armour but weaker weapons; and so on. Much of this is due to the same formula being applied across the genre, but many of these conventions make sense when it comes to building  a balanced game.

Many of these categories I'm describing are really quite arbitrary. Many of these classifications clearly overlap, and I'm sure you could rearrange them differently and come up with your own types that you could use to make sense of all these different units and the different roles they play.

StarCraft Marines hold a choke point
This refers to the lone soldier unit, be it a marine, a robot, a rabid wolf or any other lone creature that fits the game's storyline and is used as the humble footpad for your forces. Infantry forms your most basic fighting unit you can churn out without the need for upgrades or tech's. They're usually very easy and cheap to produce and offer some initial protection as the game gets underway. Individually though, they aren't much chop: they're armed with a basic gun and a few health points and not much else. As units that get right into the heart of the action they die at the drop of a hat. They will be quickly outgunned by most other unit types once things get underway and you'll find that infantry bears the brunt of most enemy fire and has the highest attrition rate in the game.

However, in numbers their combined firepower becomes formidable and you should always think of using groups of them. Infantry is light, cheap and highly mobile. Its like your force's Spak-Filla, quickly filling in breaches, scouting the map, escorting valuable units and forming buffer zones around your precious hardware. They can be used defensively or offensively, and they can challenge any unit, except for anything underwater or underground. You really can't do without your troops!

Infantry come in lots of shapes but only one size: small. Some games make a point of equipping infantry with different weapons: maybe rockets, grenades or anti-air missiles, and as a result they start to perform more specialised roles. Even so, each of these different infantryman will represent the cheapest and weakest version of that type of unit, and you'll probably find a bigger version in the form of a vehicle, ship or plane in your force.

Infantry can also be roughly grouped in several classes.

Melee Units fight hand to hand. They tend to be very strong and heavily armoured simply because they have to walk right up to the enemy to engage them - and by the time they've reached their opponent they're sporting a lot of arrows, bullet holes or acid burns. Examples would be Swordsman, StarCraft's Zerglings and Zealots, or any kind of one shot Kamikaze unit that charges the enemy and detonates on impact. They're often found as medieval soldiers, rabid monsters and giant bugs or some other non-industrial form.

Ranged Units probably form the majority of infantry types, especially in games set in modern or future times. Any dude with a gun, quiver or throwing weapon is a ranged unit. They have the advantage of opening fire at a distance. Often they'll be weaker both in armament and armour since they can harm targets at range.

Defensive Units specialise in repelling regular infantry types: classic examples abound in historical games. Phalanxes, Skirmishers, Pikemen or Spearmen have better repelling abilities than outright attacking skills. These guys form a defensive huddle, with their long weapons skewering any melee units that stray too close. Modern infantry tends to be all alike once shootin' irons hold sway.

Scouts are lightly armed and lightly armoured troops that rely on stealth and/or speed to avoid trouble. Their primary role is simply to explore the map and to keep tabs on any changes out there. Scouts are often expendable and very cheap, but will have better visual range than their comrades. You can use them to immediately get your bearings on the map when a game starts. You may not build many of them since their fighting ability is probably even less of your regular infantry, but a small investment in their spotting skills can help prevent defeat later on. Forewarned is forearmed, but directing scouts can involve a little bit of micromanagement; as lookouts they're often deployed singly. For skirmishes however, parties of scouts can be sent out on small raids on remote enemy outposts to pick off lone resourcers or unfinished expansions. Their speed in a battle is often used to distract enemy fire.

Spies are like Scouts, except they can disappear from view or remain hidden from the enemy in some way. This advantage tends to make them a little pricey and more valuable. Spies can penetrate enemy lines where regular scouts would be quickly discovered and killed. Another variation is the Sniper who is a stealthy unit that assassinates other infantry at long range. Hidden units with long killing reaches tend to shoot very slowly and appear at the expensive end of your economy. Snipers are used to harass and slow your foe down, not stop them. Once discovered they lose their importance and are quickly dealt with - and require a fair bit of micromanagement to manage in the first place. While you can quickly explore the map by directing Scouts with the minimap, Snipers and Spies need your direct attention on the main view to hide them in the battlefield.

The first major advancement for your force's tech tree is often the use of vehicles - usually expressed in the form of a Tank or some fast scouting Bike or Buggy of some kind. Basically, these are heavier, stronger, and more expensive versions of infantry - and in terms of function, come in more shapes and sizes than you can shake a stick at. They're generally the dominant life form on the ground, and the heavy versions often pack the most firepower and armour in this theatre (outside of specialised artillery) while light versions make for scouting or skirmishing. They come in several phyla:

Two destroyers cop a serving
Tanks come in every size and shape, but generally they form the striking arms of your ground force, either as mobile artillery, heavy support or just a bigger form of an soldier. They're the staple of any strategy game set in modern times. Variations on the tank include armoured cars, half-tracks, and the armoured personnel carrier (APC), which can also double as a Transport.

and Buggies are light fast scouts or high speed skirmishers. Often in games they're some kind of hoverbike, trike, all terrain Jeep or exotic hover speeder. Like most scouts, they're lightly armed and often expendable, and probably the first kind of vehicle you can build.

TA Power's custom Raptor mechs unit for Total Annihilation
Mechs are giant robot shaped vehicles that were popularised in BattleTech but have become a generic unit type in themselves. Heavily armed with high-tech weapons, armoured like a battleship and the size of a small block of flats, Mechs stride across battlefields like robotic Goliaths. They're the staple of Japanese anime and manga; inside each mighty mech is a small human pilot. While completely impractical in terms of modern warfare (I mean, really! Astronomical maintenance; pit traps; or a Muhdjahadeem with a rocket launcher aimed at an ankle joint) they nevertheless embody a romanticised high-tech ideal of what future warfare might be. Its a peculiar cross between the honour and valour of knights of old with the ugly sterility of a cluster bomb filled with rusty nails and petrol jelly: a terrifying weapon of mass destruction in heroic and anthropomorphic form. Still, for all that Mechs make excellent RTS units. They fit the bill for a exotic, highly destructive but expendable drone very well, and look pretty spectacular in action.

Hovercraft are not that often seen in RTS, although in Total Annihilation's Core Contingency add-on they made a huge impact and added a whole new line of strategy to the game. Hovers are completely at home on water or on land, and ideal for island or swampy river maps where both ground forces and shipping are disadvantaged. However, Hovers flobbling about on their inflatable skirts are rarely as heavily armed as a full naval force, or quite as nimble on dry land as infantry.

Cavalry are the tanks of non-industrial games like Age of Empires or WarCraft. Cavalry is exclusively any unit that looks like a rider on a horse (or similar creature). Cavalry is generally a harder hitter and a faster mover than infantry - representing a historical fact that ancient armies with horses had a habit of completely routing any poor sods on foot. Mobility is its best attribute, and for many games horseman make the best early scouts. Apart from scouting, cavalry is limited in the number of forms it can take (unless you enter the realm of the fantastic and stick dwarves on wolves or Heavy Metal babes on giant pteradactyles...but that's another story.); heavy cavalry usually turns up in the form of a Knight - the Medieval equivalent of the Panzer Tank. Age of Empires II has easily the best range, including scouts, mounted archers, Knights, Camels (anti-cavalry cavalry) and those power housing War Elephants.

TA's infamous long range Big Bertha turrets
Artillery is an exclusively ground based (unless you count big naval units) that can shell your opponents beyond visual range. That is, you can flatten targets at long range well into the Fog of War, provided you can actually find them first. Some games may allow you to shoot at empty patches of ground, so you can take a punt where the enemy might be and fire off a few pot shots to find out.
The advantage for you is that your enemy won't quite know where those shells are coming from, since there's a good chance those shells are appearing out of the Fog of War on their display. Unless they have radar or some way of quickly finding out, they either have to retreat their position and send units blindly into the field to locate them. And of course, those units are blundering around under your guns.

Artillery fire is immune from most obstacles by being able to shoot over hills. Its basically the ultimate way to blast an entrenched enemy out of their hidey-hole, demolish a base at a safe distance, or function defensively to break the back of an incoming horde long before it comes into your defenders' fighting range. Its vital for breaking deadlocks and in strategy terms, its an effective way of forcing your opponent to move when you want them to and a method for reclaiming the initative if you've lost it.

Artillery units are generally extremely powerful against anything on the ground or sea, but in compensation will be expensive, have little or no mobility, a very slow rate of fire and be helpless to aircraft and attacks at close quarters.
Trebuchet's: the terror of castles everywhere
They essentially a support unit that sits at the back, relying on range to shoot over the heads of your troops to hit enemy forces from afar. As a high value unit, artillery requires constant escorting and maintenance, since it can never get out of the way of trouble. That is, never consider using artillery on its own - or as a be all and end all in itself. But for all its shortcomings it provides the main muscle of your offensive and seriously debilitates your enemy, both militarily and psychologically!

Not all artillery is a big gun or a catapult. Some games offer nuclear silos and rocketry which fulfil the same role. You can also include any special magic users or heavy weapons that can shoot from afar. Easily the best examples can be found in Total Annihilation - the long range Big Bertha and Intimidator cannons can smash targets halfway across a medium sized map. Artillery counters walls, fortifications and choke points and of course, your enemies' morale!

Aircraft are units that fly through the air: in flat 2D RTS maps this means they fly at the same altitude above land and sea as if skating on an invisible glass sheet raised above the map. While ground and sea units can easily get grid locked, aircraft seem quite able to stack up in the sky in great clouds. This is fantastic for focusing stupid amounts of firepower on a terrified target - but it leaves them dangerously exposed to anything that can shoot back with splash damage.

Air power has the inherent advantage of unrestricted mobility and speed, freed from earthbound obstacles and traps on the map. Since this single attribute pretty much gives it an insane advantage against just about everything else you'll often find aircraft have been tweaked to be lightly armoured or lightly armed against ground units, or that powerful anti-air weapons will be available to your ground forces. In terms of bang for buck, aircraft are fairly pricey. They'll sit a fair way into a game's tech tree or require their own special lines of research and upgrades, needing a specialised aircraft factory or an airfield to build them.

As scouts with unrestricted vision, aircraft are unequalled: they're usually the fastest units in the game with the widest field of view, able to fly as the crow flies in any direction. This can have drawbacks though - aircraft can be drawn into a trap to be destroyed in seconds before you twig to what's happening, and sending orders to units that can cross the map so quickly can make them tricky to select with the mouse and awkward to coordinate with sluggish ground units.

Tally ho! A flock of F22's look for trouble in the World Domination custom mod for Total Annihilation. (TA fans can find this mod at TA Designers .)

Aircraft come in four major species, determined by function. Fighters, Bombers, Scouts and Transports. Fighters hunt other air units, but have little effect against the ground; Bombers pummel the ground, but are susceptible to other aircraft; Scouts are disposable high speed, lightly armed units that can rapidly survey the map, and Transports can pluck units off the field and get them in and out of hard to reach trouble spots. Naturally, there are more permutations than you can poke an AA gun at: fighter-bombers, ground attack fighters, stealth bombers, attack helicopters, spy eyes, etc. Air transports tend to carry less than their ground based counterparts and appear as hovering dropships (inspired by the movie Aliens) or a Helicopter Gunship that can carry troops. Aircraft can be versatile platforms for just about everything except artillery. Its rare you get a large, heavy monster air unit unless its representing a spaceship, Zeppelin or some fanciful flying base.

Naval Units
Age of Kings' medieval naval units
Naval Units only appear on water and nowhere else. Funnily enough. Like aircraft, they'll have their own specialised factories - a dock or shipyard - and their own line of researchable tech's. and upgrades separate from other units. They have the perk of never having to negotiate obstacles: RTS water is generally quite flat and never seems to suffer bad weather or nasty reefs. Unless the game deals with undersea terrain or arbitrarily puts some ornamental rocks in it, the only thing that stops shipping is their own awkwardness or being sunk. As a rule of thumb ships tend to be bigger and meaner than their mobile land counterparts, combining artillery with heavy armour (e.g. battleships, carriers, etc) and tend to be more expensive. However, since most games favour land bases, you'll find that while a navy can break your foe's back, it won't necessarily win you the game.

Naval units can cover two domains: sailing above the water and lurking beneath it. Submersibles are often invisible from the surface to all except spotters or specialised sub-killers, and can be immune to ground and air units fire by virtue of being underwater.

Surface shipping's functions is usually determined by size and speed. Small boats are often patrol boats: small, lightly armed scouts or gunboats. Mid range sees the escorting destroyer (a ship killing ship) designed to protect your bigger and more expensive ships; missile frigates, anti-air ships, mine layers, support ships, submarines, etc., anti-air ships, mine layers, troop transports, support ships, etc. Mid range boats seem to present the most roles, while the heavy end of your navy usually boils down to either a whopper of a battleship or an aircraft carrier. Battleships are usually just giant bombardment machines, and carriers will perform a air service role. Frequently these bigger units will have little means of defending themselves.

StarCraft's busy little SCV's
By far the most important units in your arsenal are the ones with no weapons: your workers and support units. These guys make everything else possible and without them there is no economy, no building and thus, no army. Protect them at all costs. They form the heart of your force and also pose its greatest weakness. In most RTS games this support is reduced down to a single unit, a Worker or Villager of some kind. It has at least three basic functions: resource gathering, construction of buildings and defences and repairs.

Workers work best in large gangs. They're invariably the first unit unit you can build without any prerequisites.

Homeworld's Harvester asteroid mining
The other form of worker is the Harvester unit, as seen in Command & Conquer or Homeworld. Harvesters are large vehicles that trundle off on long expeditions looking for resources to scavenge, only returning to home base when full or the map has been picked clean. While gangs of workers generally work around the one spot and form the heart of a base, Harvesters are loners that roam the hinterlands of the map all on their own. This makes them magnets for trouble. Harvesters generally carry large hauls, are unarmed, and often weighed down with tons of armour. They require constant vigilance and looking after. This is a unit that runs almost entirely on a computer driven AI; and rarely does it pick the best or safest route, it might wander right across the map to collect a teaspoon of ore or mindlessly work its way into the waiting guns of your enemy's base. Harvesters are highly prized both as an economic asset and a juicy target - and taking out a couple can seriously hamstring an opponent.

Support Units
Total Annihilation's patrolling construction planes
The close cousin of the Worker is the Support Unit. Support units provide an indirect source of strength, rather than a direct one. Support units are helper units who work best when they have someone they can offer their services to. They enhance your existing units, but are largely useless on their own. They come in two rough forms - Civilian and Military.

Civilian support usually means an assistant, medic or repairer of some kind. While not actually armed or directly involved in the fighting, and sometimes incapable of starting any building projects or attacks, they can still be the decisive unit that can turn the tide of a fight by simply keeping other units alive for that little bit longer, or assisting in construction. Support can come in the form of a supply ship, a refueling depot, a roving repairer or medic or a shield battery that recharges failing force fields.

Military support units often have some non-hostile spell that enhances the strengths of the armed units around it or some kind of weapon that may not in itself be that useful in a one on one fight, but if used with your regular forces can quickly swing the battle in your favour. It might be a wizard generating a magic shield that wards off bullets temporarily, or cast invisibility, or double the attack strength of certain units for a short while. Sometimes a support unit may be just another guy with a gun - but used to their best if they are actually kept away from the action. For example: artillery could be classified as "support". Your units on the front line can be supported by some long distance shelling to soften up the opposition before your fighting units directly attack it. While the rest of the team actually gets down to some hand to hand, there might be a support machine gunner simply firing in the the general direction, weakening the opposition to make the attackers more effective.

A transport is a large mobile unit that can carry one or more other units. These are another sometimes under utilised unit that can perform absolute wonders for your force and your economy. They get around problems of accessibility on the map by carrying many units across impassable terrain (like an ocean or a mountain range), or cart large numbers of units quickly and easily to surprise the enemy. Classic examples are the Transport ship, the armoured personnel carrier and the Dropship. Sea going transports usually carry a lot of units, and are excellent for moving huge numbers of units and workers to new islands; air and land transports are often smaller, and designed to move units across a map quickly.

The benefits of massed or high speed transports are offset by two things: firstly, most transports in strategy games are unarmed - and the units within them can't be used to defend them either; and secondly, if a transport gets shot down or sunk, everyone inside is killed, too. On top of that, there is usually a high degree of fiddling loading and unloading large numbers of units at a time. The fuck up factor figures highly in transporting especially under combat conditions! If you're staging a big transport invasion, you must have escorts to soak up a bit of damage, enough space to offload your troop, and enough coordination getting it right. You'll probably need to practice.

An invisible Observer surreptiously surveys an enemy base in StarCraft
These are specialised units that do little more than spy on the enemy or keep an eagle eye out for spies and enemy attacks. They provide an essential service much like a Support Unit, but the strategic element of reconnaissance and intelligence gathering on the map puts them in a class of their own. Scouting is a vitally important but frequently under-utilised line of strategy by beginners: scouting the map and maintaining a constant eye on things at all times is essential. If you don't know what's going on, you can't prepare for it properly, and in grave danger of all your forces being trumped and wiped out on the field. This might involved nothing more than positioning a few single units around the countryside, since anything that has eyes can scout, but in some games you have to deal with units that can cloak so specialised spotters must be deployed to counter invisible or stealthy units.

Yellow spots blue on Total Annihilation radar
Spotters can simply be any unit that "spots" on behalf of another unit. Artillery can destroy targets far beyond their visual range, but you'll need a second unit to sneak ahead and locate targets, unless you like firing blind into the Fog of War. In some games you can build radar, which picks out enemy units on the minimap that lurk outside your units' collective visual range - another indispensable tool for directing long range artillery with. This radar coverage can be countered with special anti-radar units. There's nothing worse than going in blind: you'll miss valuable targets, flanking manoeuvres or ambushes; and there's nothing more terrifying than trying to defend against units you cannot see - most games won't let you target invisible units - unless you're able to target the ground under them and hit them with lucky shots and splash damage.

Magic Units and Spellcasters
By magical I don't just mean hocus pocus but any special ability that goes beyond the normal point'n'shoot of your standard working grunt. It might be the obvious tinkerbell zap that peels the skin off Orcs and messily turns them inside out, or it might be simply a spell that heals another unit, or induce an adrenalin rush (like a Bezerker mode for a barbarian), or a one shot EMP (ElectroMagnetic Pulse) blast that freezes robotic enemies temporarily or a cybernetic upgrade to an atheistic cyborg. In a sense a spaceship, a robot or a Airforce Ranger "painting" a target with a laser sight could be seen to have "magical" abilities - abilities that perform the same strategic role as magic outside the obvious fantasy context.

Magical abilities are there to basically extend your units' capabilities beyond the usual move'n'shoot and add an extra, strategic element to a game. Sometimes its a "live" effect, like a force field you can turn on or off, or a medic automatically healing units or maybe a cloud of poison gas or a magical storm of hailstones. What usually differentiates these types of units from the normal ones is that their special abilities are usually enabled by hand: that is, more often than not, its you the player who has to order the use of a special attack or power. Regular units will engage anything and everything that strays into range, but spellcasters and special abilities will stand around doing nothing until specially ordered to do their thing. Spell casting is basically a micromanagement thing; so you'll see tonnes of it in Blizzard games like StarCraft or WarCraft.

Heavy Weapons
If you made it to the end game and your economy is booming but your foe is still a major headache, then its time to wheel out the big guns and go for the grand finale! These are the really advanced units found at the end of a tech tree, often the most devastating and the most spectacular to use, and the payoff after all that work. They might be nuclear silos, whopping great battle cruisers, a Godzilla class battle mech or some other monster that specialises in Armageddon. Either way, the game's about to go out with a bang!

But even here, these giant trump cards at the end of a build will still have caveats to balance them. If you do have a titan that seems invincible, then you'll invariably find the sheer effort and time it takes to build it is where the balance lies. By the time you've finally ground one out, the enemy might be all over you like a rash with hordes of cheaper units. Consider that Homeworld battle cruiser in Distributed Force. As is often the case with mega units, it will be slow and ponderous. For all their power, they can usually only hit a couple of targets at once - so a titan facing off twenty smaller pissy units may actually be in real trouble...by the time it finally works its way slowly through all those annoying gnats, it might have lost a significant amount of health to a bunch of quickly built, quickly deployed fast firing units. Most titans will need escorts of some kind to get the full value out of them. However, if you do find yourself with a game that gives you ridiculously powerful units for little cost, then you've probably found a RTS title that's going to get very boring very quickly. (Or you're playing a custom mod!) Either that or your foe is a complete dill for letting you get to the endgame with such a lopsided advantage.

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Last modified Sat, Apr 2011 by Lindsay Fleay