attacking the enemy home world

SUPERWEAPONS!! Particularly the TEC Novalith or Vasari Kostura. Novalith- Straight-Up BOOM!! factor. 2-3 shots and the enemy planet is DEAD.

Kostura- I'm not sure if this works in vanilla 1.17, but in Entrenchment the Kostura will create a Phase Stabilizer Node at a planet. Which means if you have a Marauder/Orkulus with the Stabilize Phase Space ability or a Phase Stabilizer, the fleet it accompanies (or the fleet at the Orky's loco) will be able to jump at the Kostura's target.

and if the enemy planet is dead, do the enemy still go banzai all over your forces in that region?

in other words, will they try their hardest to get the home planet back?

Like anything, you need up-to-date intel to know where the enemy is at all times so you know when they will be joining a battle.  There are a couple of good options you have here.  One is to split your fleet into two groups (unless you're Advent, which gets a lot of benefit out of sticking together with multiple capital ships, there's nothing wrong at all with sending half your fleet with one capital ship and half your fleet with another).  Find out where the enemy fleet is, and then attack the opposite side of his empire.  Once his main fleet moves to deal with your first attack, launch a second attack with your secondary fleet.  Any time he's about to warp in and join a battle, retreat the fleet that is fighting there back to your defenses.  The AI doesn't know how to deal with this, so while it's running after one of your fleets, the other returns to attacking his flank.  He'll keep running back and forth until he has no planets left.

Another option when bypassing is to focus on structures and ignore the planet.  This is especially true with the AI, since they often buy far too many planet hit point upgrades.  Destroying a few labs and trade ports can set them behind massively.  This is best achieved with carriers loaded with bombers.  Entrenchment adds anti-structure frigates, but I still think bombers are the better pick for this purpose because they're also useful in battle, whereas those anti-structure frigates won't help at all in a straight fight.

The final option is to try to rush the planet, bring down its hit points, and then colonize it quickly.  Build a frigate factory and several repair bays quickly.  This combination will give you the defense edge you need to hold the location.  You do need to ensure culture will not be an issue, and you'll need heavy bombardment capabilities to deal with a planet quickly.  If it has 4500 or more, this really isn't a viable approach unless you've got insane firepower.

The AI has a tendency to retreat when its outgunned and preserve its fighting strength.  Often times this means it's digging its own grave because it's not defending the last scraps of economy it has left, ensuring its army will remain weaker.  However, it does drag out the game.  One thing that's always worth trying to do is to "lure" the AI fleet into a gravity well with a phase jump inhibitor, and then trying to wipe it out completely in a single attack.  This will allow you to overrun his empire (don't waste time colonizing anything, you can clean up his feeble attempts to pick up the ashes afterwards with ease) without facing further resistance.

My final piece of advice is not to be afraid to fight with fewer capital ships or smaller armies.  It takes time to become a good judge of fighting strength, but eventually you'll find that judgment and the confidence to launch early offensives. 

No, the AI becomes remarkably timid when you start capturing its planets.  This can drag things out (after all, it's sitting in the defensive and forcing you to fight it where it's strong, and then taking cheap-shots at you if you leave anything undefended), but in the long run ensures the AI's defeat.

Depending on the number of defenses the home planet has, I have had good luck with this strategy. I use my main force to attack a nearby colony. When the enemy comes to defend the colony I dispatch  6 or so seige ships, with an equal number of fighter transports for cover, to destroy the homeworld.

 Another question is whether you are simply trying to destroy the homeworld or to conquer it. Destroying is easy and busies the AI trying to reclaim it.

 If you have Entrenchment you might also try slapping up a starbase at a nearby colony. The AI will throw alot of its firepower at the SB, freeing you up to attack the homeworld.

 If you don't have Entrenchment get it. For 10 bucks it adds 30 bucks of enjoyment and strategy to the game.

-Ghostwheel

Another possible problem is fleet composition. What types of ships do you have in your fleet? If you have light frigates and the AI has long range frigates or heavy cruisers, you'll get slaughtered. It could be you're using inferior ships, or that you simply don't have enough ships for the fight. Especially if you're playing as TEC aginst an Advent, you'll want at least ship number parity. Given that Advent ships, especially the illuminator, are stronger than TEC ships, an advantage never hurts.

- Yakov

In many cases, the AI will attempt to recall all of its ships to its HW in order to try to save it.

Empires without a homeworld will result in all of its planets to having a maximum alleigance of 35%, so any planets above that will lose alleigance until they drop to 35%. The AI simply designates one of its remaining planets as its new HW (if any are left) after you destroy the current one.

There are a lot of reasons why you are losing, probably either due to fleet composition or size.  Just remember, when you jump past the outlying colonies to attack a homeworld, you have to be positive your fleet can dominate the enemy fleet and defenses.  The enemy fleet has the benefit of defensive structures, culture bonuses, and is getting new reinforcements built locally that are joining the fight.  If you have jumped past some worlds, it is not easy to reinforce your fleet to keep up with the enemy reinforcements.  If it was a close fight to begin with, attrition will soon tip it in the enemy's favor.

I say send in a diversion fleet of super heavy armor ships, like the kodiack and the cap ships and attack where they are gather up. Usually before I fight them at their homeworld attack their other worlds, keep them busy at the front worlds instead

I was playing against a hard advent the other day and took over one of its asteroids.  It continued to try to take that asteroid back even when I conquered planets further into their empire.  Strange how the AI can sometimes have tunnel vision about one particular planet.

If you're using more than 4 siege frigates, just buy a siege capital ship (Marza or Vulkoras for TEC and Vasari.  Advent are out of luck in this regard).  The siege frigates are so fragile that it's worth pitching in a little extra cash for something that's hard to kill.  Remember that if there's even one hanger, your siege frigates are pretty much screwed, but that doesn't mean anything to a capital ship.

It often gets tunnel vision about specific planets.  I once even saw it get tunnel vision over a neutral, sending its entire fleet to chase two Vasari scouts running back and forth between different gravity wells.  I kept its capital ship and 40 cobalts busy for nearly half an hour with these antics... all chasing two scouts.

THAT IS HILARIOUS!

i watched my replay. seems like what i didnt see was their capital ship factory built TWO capital ships while i was attacking their other factories. so now i know i need to destroy at once the capital ship factory and bring in some heavier ships. i had a kol class ship, that carrier class ship and one other kind, i forgot which one.

and i didnt bypass any enemy planets, btw.

thanks for all the help. i will definitly try to make a diversion, maybe in another system even.

you could use culture... (if you have about a week or so)

I've got into the habit of creating a network of Deliverance Engines when playing as the Advent; they're arguably not has powerful as the Novalith or the Kostura, but if you either have three or four strike one planet (if the planet has many phase lanes to enemy planets) or spread their fire (if the enemy isn't so clustered) you can normally turn the game into a matter of time before culture causes them to lose control of most of their planets and you can mop up whatever's left. Maybe try that if you play as Advent?

Speaking of Deliverence Engines, how big boost does it gives to your fleet in the grav field, when you shoot it?

The Deliverance Signal increases the damage output of your ships by 15% in vanilla Sins.

As for Entrenchment, I've heard its higher.

The TEC carrier is pretty much useless. For three caps try a Kol, a Marza and a Dunov. Make sure your Kol as at least level 2 Flak Burst for air defence, the Marza Raze Planet, and the Dunov Sheild Restore.

Think of the tactics as being like chess - go for the pawn sacrifice. Spam one or more of the outer planets with colony ships and seige frigates, the AI will go bananas trying to get there! You can then jump in, flatten the home world, then jump out before the enemy fleet can get back.

I know this might more unorthadox but along with your huge fleet of ships, bring like 20 colony ships too, AI loves colony ships. So when AI is attach your colony ships pick off the other ships fast. And have like a fleet of your repair ships deticate themselves to healing your colony ships instead.

u know what would help(and I did this once) make at least 5 novaliath cannons if ur playing TEC so u can just keep fireing, boom, boom, boom, boom. Thats the most pleasing way to win in my opinion, espesially when facing 6 AI's.

Although undeniably powerful, superweapons aren't always a feasible strategy to undertake with the cost of labs, research (including prerequisite research), and planets (for logistical and tactical slots).

On a related note, I did once build almost 20 Novalith Cannons spread in two systems and proceeded to bombard a third system with all the surviving AIs in it by enabling autocast on all of the Cannons. None of them lost as a direct result of this bombardment, but through the cost of reestablishing colonies, neighbours attacking them after a hit, or me coming in to mop up the rest.