General rule of thumb:
Any time terran expands, they are vulnerable to attack.
Any time you have a tech lead, you may be able to attack.
Just because you can attack doesn't mean you should. Not every attack will end the game, but some will cripple your opponent and make the game easy to win. Most games won't have to go to broodlord infestor for you to win if you can identify the correct moments to attack.
Here's a few examples:
Terran grabs an early expansion:
- Small swarm of lings (12-20, preferably when speed is finishing if you went 16 gas).
- Ling baneling (Hits later then the speedling pack, easier to counter with hellions. Useful if they delayed tech in favor of a proxie 2 rax expand).
- Roach Ling (4-7 roaches, make lings while moving across the map). Countered by bunkers
- Roach ling baneling. (Puts you all in, Terran must scout it and have good building placement/reaction to survive.)
None of those attacks have to win the game, but the more you invest the more damage needs to be done. All of these attacks can be stopped, but they work at all skill levels, even pro. If a terran does a 3 barracks wall, it's usually best not to attack, though you may pick off addons if they are sticking out.
Reading your opponent and responding properly makes a big difference. Similarly denying scouting or misleading your opponent is important. If they think you went 3 hatch they won't expect an attack, you could cancel the 3rd hatch and go all in. Deception requires a certain level of competence on your opponents part so it may be best to skip until you know your opponent will scout.
When terran takes a 3rd base can also be a good time to attack, but the longer the game plays the more generalized our suggestions have to be. The best advice is to scout expansions so you know when it's happening and can choose to attack if you want. Denying expansions (overlord goop, burrowed lings) can win games. When you see your opponent trying to expand, you attack and draw their army out of their fortified position. Having an extra 30 seconds to respond is huge.
*In the last MLG Startale's player Life showed great use of zerglings by sending his initial zerglings to his opponents 3rd base. When they had hellions moving across the map and went to expand, he denied the expansion with his 6 (may have been 4) lings and forced the hellions back to terran's base. This is normally when zerg would be defending against hellion pressure and trying to deal with the early creep contain terran applies.
You don't have to invest a lot into your attacks to make attacking worthwhile.
A tech based attack timing would be:
- Roaches hit the field (counter hellions/poke the front)
- Mutas hit the field. (hit their SCV line before they have turrets up)
- ling speed finishes (you now control the map until hellions are out)
- Baneling speed finishes (if they don't have siege tanks or marauders punish them)
- INFESTORS (not a required timing, but landing a few key fungles on a marine group can set you up for an easy 4th base).
- Ultras pop out (don't give them time to make lots of marauders if you don't have to)
- Broodlord deathball.
- Drop finishes
- Burrow finishes (burrow some banelings and entice their army to move over them by luring them with mutalisks or other units)
Just because you have the tech doesn't mean you should attack, but if you think you can do damage go for it. Only by trying will you learn what works.
Edited by Kaz on 11/14/2012 12:34 PM PST