Terran Vs. Terran
Defending
*Against large fleets of Battlecruisers(which I have seen built MANY times) you have several options. 1) Use your own fleet of BC's. 2) I like to keep my Ghosts inside of Bunkers and when you see a large fleet of BC's or whatever get them out and use Lock down. Lockdown can be the greatest thing that ever happend to you in this case. And then move your air attacking units in for the kill. If you have Marines Stim Pack them to kill the BC quicker so the Lockdown won't run out. 3) You can build large fleets of cloaked Wraiths. If the opponent doesn't have a Sciense Vessel and isn't good at Sweep Scanning then you will have an easy victory.
*Against massive fleets of Tanks you pretty much have to build tanks yourself. You should still use other things like Wraiths, Lockdown, etc. but those alone won't kill 3 fleets of Tanks. If you have a Nuke you could use that to either scare them away while you build some stuff or since tanks are slow you can blow some up if they don't retreat. Either way you need Tanks.
Attacking
*To take out Turrets, without being harmed, you'll need a BC(with Yamato) and a Sensor Sweep. Sweep the place you think that there is a Turret and move in to Yamato it and one Yamato will destroy it and you won't get hit.
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