On fast speed, turn 30 is about the time when it becomes possible to commit and to benefit from serious aggression. You've got your basic infrastructure set up, and so does your neighbour; if you take their planets you're getting more than you'd get from an outpost. You've had the time to build a fleet and so have your neighbours. Plan to either go to war by turn 30, or to become the best of friends with your closest neighbour by turn 30.

Broadly speaking, you can usually have 2 new colonies up by turn 20. These colonies, as well as your home system, should have the basic infrastructure of Cerebral Reality, Drone Networks, Xeno-Indusrial Infrastructure, Public-Private Partnerships, and Big Data Shipyards built or close to it. Get an Eco Behemoth for the mobile Industry boost as well if you're having trouble getting all this stuff; build it blank, then refit it with dust. It will then take about 1-2 turns per ship, so if you start building a fleet around turn 20 you can have built about 5 combat ships from each colony before turn 30. This is the basic setup for being aggressive or defending against aggression; you have the science to research military ships and enough military techs to get 14 CP cap, and the industry to build enough ships to fill up that cap and create a powerful early fleet. Whether you're intending to invade your neighbour and take his stuff, defend yourself from early aggression, or just to deter any aggression and kill pirates, this is a solid and strong strategy.

By turn 50, people will probably have carriers. Plan accordingly.

Supremacy is the most common multiplayer victory type because of how it interacts with alliances. Most other victory type thresholds scale upwards with the number of people in your alliance; the economic victory requires your alliance to make more dust the more factions are in it, the conquest victory requires your alliance to hold more systems, etc. However, the number of home systems cannot increase in this manner. In fact, supremacy gets easier the more factions are in your alliance, as your allies home systems are obviously counted as home systems held by the alliance. Every allied home system is a home system you don't have to conquer. As the maximum amount of factions in an alliance is half the factions in the galaxy, if you have the largest possible alliance then each alliance member only needs to take and hold a single home system that isn't their starting system. This is why the supremacy victory is the fastest and easiest victory type. Because of this, games generally turn into two gigantic alliances fighting each other over the home systems. Pick your allies well and you're already halfway to victory.

Sneaky conquest victories are less common but still happen. Someone will colonize 10 systems in a turn or take over a bunch of enemy systems and win before the happiness penalty has time to cripple them. The other victory types effectively don't exist. Economic victories are the third most common, but still extremely rare.

Military power, tactics, and strategy is thus of the utmost importance. Becoming skilled at fleet and ground combat is necessary to compete.

All factions have at least one small ship that has at least four support slots; either their colonizer, explorer, protector, or at the very least their upgraded protector. Proper use of these ships can decide games.

Dedicated exploration ships with 3 engines and a tier 1 cloaking module are extremely cheap to make and very useful. You can set them to autoexplore and they'll discover the whole galaxy for you, or send them poking around enemy systems to look for ship buildup, or scout for behemoths to take out. Anticloaking modules are expensive and people tend not to research them until someone starts using cloaked ships aggressively, so it'll take a while before these ships get discovered and cleared out. And even then, they're cheap enough to send on suicide missions into enemy space to scout their ship designs.

On the other hand, even an exploration ship with a single gun is capable of guarding a system. They're not going to kill anything that's combat-capable, but a guard action with level 1 anticloaking will shut down the aforementioned cheap spy ships. This will also prevent an aggressor from moving more than one system at a time into your territory, at least until free-movement becomes cheap late in the game.

The first step to building proper ships is to research Ubiquitous Surveillance and build Big Data Shipyards before you start manufacturing ships. Additional EXP on ship creation is crazy good; Big Data Shipyards will give your ships two additional levels at creation, boosting the HP of your ships by 40%. This is a critical building for doing any kind of early combat at all.

Disregarding defensive modules for now, there's a basic weapon-loadout triangle; full missiles > full energy > 1:2 ratio of slugs:energy > full missiles. Missiles have the highest DPS in the game and 100% accuracy at long range as well as cross-lane, so in the first phase they'll kill enough ships to turn the entire fight if they aren't countered by kinetic flak. Kinetic slugs mount flak weapons that shoot down missiles, but are only good damage at medium or close range and are useless cross-lane, so you need some energy weaponry for reliable long range damage. Finally, going full energy weaponry lets you stay at long range and shoot down fleets with kinetics before they can get close.

Returning to defensive modules: to summarize, plating modules grant more HP and percentage damage reduction against projectile weapons, and shields grant much more HP than plating but only against energy weaponry and with no damage reduction. Projectile weaponry has much higher potential DPS than energy weaponry, but suffers from unreliable accuracy and plating modules allowing the stacking of extremely high amounts of damage reduction. Shielding is worse against energy weaponry than plating is against projectile weaponry, but energy weaponry has lower potential DPS.

Lone ships are always in the centre lane. An unescorted Military Behemoth or Ark is easy prey for a fleet with enough ships to have access to the top lane. Based on the range profile of the lone ship's weapons, you can choose to have almost all of your ships engage always at long range from the top lane, or all in close range in the middle lane. This is why lone Military Behemoths are useless; they're always counterable at the tactical level.

Bombers are strong against large and medium ships; they're primarily a counter for other carriers, but in enough numbers they can swarm down medium and even small ships. Fighters shoot down bombers well, and flak is also somewhat effective. Squadrons can only be mounted on Coordinators or Carriers, so if you're planning to use bombers as a counter to Carriers you're going to at least want Coordinators.

Boarding pods let you steal enemy ships and use them for yourself. So if the enemy has nothing good to steal, they're useless. If you're lagging behind tech wise and the enemy has better ships than you, boarding pods can let you steal enough of theirs to fight back until they wise up and build their fleets to counter boarding pods. Boarding pods are shot down by flak, like missiles except with more HP and lower fire rate. They fire very slowly and thus are countered by small ship spam; you can only steal so many ships per fight, no matter how large or small they are. The manpower damage effect's effectiveness is based on comparative infantry strength, so if you're using or fighting against boarding pods upgrade your infantry troops.

In short, attack ships will focus fire on defensive ships first, then other attack ships. Defensive ships will shoot at attack ships first, then other defenders, but generally don't have enough guns for this to matter. So, building your defense ships to counter enemy weapon loadouts is important. A protector or two loaded up with kinetic flak and plating can act as missile sumps to take the teeth out of missile spam fleets potentially long enough to get into medium range where they start to lose accuracy. Protectors loaded up with shields can absorb a significant amount of energy fire, but energy weaponry has much more reliable accuracy; it's probably not enough to turn a battle around if the rest of your fleet can't handle energy fire.

Refit cost is based on the difference in industry cost between the two ship loadouts. If you are simply swapping weapon and defense modules within the same tier, the cost is very low. So, if you know what your enemy's fleet is, they're in your territory and thus you have the ability to refit and they don't, and you have roughly equal ship and military tech levels, then you should always be able to win by refitting your ships to counter theirs.

Step one in knowing what the enemy's fleet is. The cheap spy and picket ships from section 3 are key here. For a very reasonable investment, you can watch enemy fleet movements and prevent them from progressing into your territory for more than long enough for you to read their ship loadouts from the military power estimate and range profiles. By keeping your ships garrisoned or cloaked you prevent them from being able to read your loadouts and build their ships to counter yours in advance.

Finally, aggression usually requires ships with at least 2 engines due to the distances involved. A savvy defender using picket ships and perhaps a hero for mobility can get away with 1 engine designs, using the extra slot for a booster or a defense module, making their ships superior in straight up combat. If the enemy is using 1 engine designs themselves, their ships are taking absolutely forever to get anywhere and are likely already obsolete.

Ground Combat is relatively simple. Tanks are better than Infantry, Planes are better than Tanks, Infantry is bad and should never be used except in desperation or against very small numbers of Planes; Infantry supposedly counters Planes in theory, but not in practice.

You need to out-kill the regenerating manpower from Draft, so you need manpower deployment modules for more troops on the ground to deal more damage. The amount of manpower a fleet can deploy without manpower deployment modules is about 600 in the early game; 600 manpower of Tanks can easily overwhelm 200 manpower of Infantry, even with Draft, so upgrade to Tanks yourself ASAP.

Immediately after an outpost turns into a proper colony, it has 0 manpower and 1 population, and thus cannot defend itself in any way. You can get a cheeky insta-win invasion on this turn.

The requirement for manpower deployment modules after the very early game will require building a dedicated invasion fleet in most cases. This is another form of defenders advantage, as the defender just has to shoot down the enemy fleet and not invade.