I've been playing Protoss for a while, and have found a way around most assaults, but then, when I tried to invade my enemy base, I was beaten back, again and again, by like 20 siege and 20 battlecruisers. Any suggestions?
Don't try going toe to toe with battlecruisers and tanks... you'll lose. Instead, rely on the other weapons that protoss gets. Combating battle cruisers can be pretty easy. A couple of templars with storm can really hurt battlecruisers and send your opponent into a frenzy. Also, arbiter's freeze really will kill them, not only because you put him at a disadvantage for a minute, for you will also kill his number keys (ctrl+1, ect.) so he won't beable to group up his ships and he will prob retreat. Also, scouts will pretty easily own battle cruisers if you have enough of them. Even 12 scouts VS 12 BC's would cause some serious damage to the battle cruisers. As far as tanks go, if the opponent is going all tanks, you need to hit them with air. But, there is another strategy i've done before. A standard defense tactic by terran is to put 3 supply depos infront of some bunkers with marines, then put tanks behind the bunkers and maybe add a few turrets. There are two ways to combat this. One is to make a few zealots, get armor and speed on them and take about 8 of them and run right up to the spply depos. The tanks shock will kill the supply depos and your opponet will be hurting. However, my favorite strategy is to group up about 12 zealots (they dont need to be upgraded) then get an arbiter and send him in above the tanks. You'll probably need to sacrvice the arbiter for this. While you're above, recall the zealots and they will cause major mayham. The tanks will probably end up killing each other. Anyways, the #1 thing you should be using is arbiter's freeze... heck, you could even just go over and freeze all his tanks, then rush him with guys....
If he masses BCs vs toss he should loose because it's not really echonomical in that MU. If he does make BCs + tanks, get high templars with storm, zealots for the tanks and some scouts for the BCs (it's the only thing scouts are good for on land maps, killing BCs and carriers) Get some goons too.
And if he doesn't tech to a tank/vult/turret tank push, u should be able to kill him before he gets masses of BCs.
You can use High templars to keep the cruisers at bay. Cruisers also take time and massive resources. Attacking thier base while his fleet is attacking yours also works well...like recalling a load of zealots/dragoons. Also freezing some crusiers and taking the rest, or any other troops works well...arbitors are really helpfull in these situations.
That would cost a lot to produce, u should have kept him down economically so he couldn't make that many. In mid-game, he HAS to use a tank push, if not, just kill him
Keep killing his tanks and destroying his expansions so he cant afford mass BCs.
Terran: More BCs than ur enemy, maybe mix in some golls too.
Zerg: Hydras in dark swarm + plague. Plague will take away 300 hit points of the BCs total life, so it is a very good counter. Devourers can help a lot too. BCs kill scourges in 1 hit so they wont do much...
Protoss: PSI storm, goons, scouts, corsairs, even statis field or mind controll... Protoss have many counters for BCs. I think the easiest counter would be simply PSI + goons.
I'm pretty sure that 12 Scouts can take out 12 BCs. You can pop out 2 Scouts by the time s/he pops out 1 BC, and Scouts deal jsut a bit mroe air dmg than the BCs. But the BCs can shoot farther then the scouts, but have a longer cooldown time than the Scouts. However, the BCs have 500hp and the Scouts 250hp.