From the strategy guide written by Stefan Sasse
A paradox in the unit system of Twilight Imperium 3 is that everyone uses the same units, but that they behave differently and have different importance depending on the race you are playing. These differences are addressed in greater depth in the races section of this guide. In this chapter, we will have a look at the general traits of the units.
Destroyer Destroyers are the smallest among the capital ships. They are commonly underestimated because they only hit on 9. But they are very cheap, so you can produce them in masses (provided you have the build limit). Plus, Hylar V Assault Laser increases their hit chance by 50% and will be researched early in 90% of the games. Another big trait of the Destroyer is the Anti-Fighter Barrage that makes the Destroyers a must if your enemies are building up to Fighter swarms. These you will then destroy even before battle, thereby making the Destroyers count even more! Smarter people than me have conducted some calculating of hit percentages and came out with the Destroyer being the unit that brings the most bang for the buck, so it’s always a good idea to have them around.
Cruiser The first ship that feels like a capital ship is the Cruiser. Like the Destroyer it is very fast (range 2, which can reach 3 with use of Type IV Drive!), it hits on 7 without the common Hylar Lasers and with Stasis Capsules it even can carry Ground Forces! For only two resources, you get yourself a highly versatile vessel that in cases of games where the opponents are tight with their Ground Forces saves you the effort of teching for XRD!
Carriers Carriers are the backbone of your fleet. You almost always need at least two of them (an exception from the rule is when you use Cruisers for transport). You will want to fill them up with Fighters as cannon fodder and you need them to carry sufficient Ground Forces for the invasion battles. Note that Carriers are not very fast without XRD Transporters, which is almost always a problem (except your production is so in the center of all events that they need not travel far), so tech them up quickly. There’s another thing to consider: if you go in combat, you should make pure-Fighter and pure-Ground Force Carriers. This way, you can feed the Carriers to the enemy once their fighters are down which is in most cases preferable to losing a unit that can actually do some harm, and you don’t lose your ground forces by doing so.
Dreadnoughts Unfortunately, this very coolly designed unit kind of sucks. It is very expensive, slow and only has a 10% better hit chance than the not-even-half-as-expensive Cruiser. For the price of a Dreadnought, you can purchase two Cruisers AND a Destroyer, which in space battles not only gives you a serious edge regarding the punishment you can take but also hit far more often. Of course, the Dreadnought is not without its merits. For one, it gives your fleet an additional hit to sustain without a need to stack up the Fleet Supply. Second, it has the ability to bombard Ground Forces, which helps invasions. And third, most people don’t understand how crappy they are and are either intimidated or dump their money in these ships instead of purchasing the good stuff they should. Oh, and they look cool. Lately, they have gotten a bigger punch with the Duranium Armor Tech, which makes them more worth the while. When you play with “Shards of the Throne” and implement the new techs, Dreadnoughts are worth reconsideration.
Fighters Fighters are not built to kill in most cases, but to take all the hits while the real fleet takes out the enemy. They can be upgraded twice, so they can hit at a 7 – and then they are really fearsome. Unfortunately, they easily and prematurely fall to the Anti-Fighter Barrage of Destroyers, so try to keep them away from armies relying on Destroyers. Should you ever get the Graviton Negator tech, you will transform every ground battle into a guaranteed win, and never forget that every Space Dock can support three Fighters. It is often not a bad idea to leave some Fighters behind so the enemy can’t easily raid your production systems.
Ground Forces – Ground Forces are the only option if you want to take and hold planets. They hit on 8 and can be upgraded to hit on a 7 (and even 6 in defense) which will give you a major edge over your opponent. Since oftentimes roughly the same small number of Ground Forces will fight each other, luck plays a major part, and the smaller your hit number is, the better your chances are. Generally you should always try to outnumber your opponent in ground battles 2:1, because luck plays such a large part on the one hand and on the other hand you want to be able to defend the planet afterwards.
Flagships Mighty units with a big variety of capabilities between the races. We will explore them in detail in the “Races” section. Suffice to say, some of them are good, others mediocre, some outright bad.
Mechanized Units Mechanized Units are the strongest units for Invasion Combat you can find. They are immune against nearly anything: PDS-Fire, Action Cards, techs, bombardments and the like. They also have Sustain Damage and roll two dice with “6”. Whenever you want to defend a planet or expect to come into ground combat, you should have them with you. They really drive up the stakes for any adversary involved and are well worth their price. A major disadvantage, however, is that you can’t take them with Dreadnoughts or Cruisers.
PDS The Planetary Defense Systems are important measures of stationary defense on planets against attacks. They fire against space ships as well as against invading ground troops. Unfortunately, the first drastically looses importance as the game progresses. Don’t be fooled by the opportunity to hit or to deflect hits that is provided by the Magen Defense Grid and the Maneuvering Jets. You will very soon have fighter cover that can eat up the hits, so the techs are seldom worth their salt for the PDS bonus alone. The important role of the Planetary Defense System is not to fire at space ships – although they deter smallscale raids like the Mentak like to do – but to fire at landing Ground Forces. Players find it often difficult to bring enough Ground Forces to the site of invasion, and when they have to carry a lot fighters as cannon fodder – per example for the Planetary Defense System – that means less room for Ground Forces. Planetary Defense System even out the odds before ground combat since they kill Ground Forces before the fight actually starts. You’ll want to protect important planets by two Planetary Defense Systems if possible to raise the effort the enemy needs to bring on in order to conquer planets.
Space Docks Space Docks are relatively simple: they allow you to produce ships. Remember that the build limit is cumulative if there are several Space Docks in once system. Never forget that you are not allowed to produce a Space Dock on a newly conquered planet and that blocked Space Docks are not allowed to produce ships. This makes sieges a viable strategy. Simply block the airspace over a planet with a Space Dock and render it almost useless. If the enemy wants to take back control without actually fighting a space battle, he needs to build Planetary Defense System and fire at the blocking ships. So one Destroyer can effectively block a system for a long time.
War Suns The War Suns are the mightiest unit around, but also the most expensive by far. It requires extensive tech to use them, and you should always build the Fighters to protect the War Suns from enemy attacks. This boosts the cost for a fully-stocked War Sun to effectively 15 resources and 7 build limit! Only go for them if you can afford it. In the race section we will see which races are best able to use War Suns. But be careful, losing them is always a major blow.