ZvT - Managing the 3-base Contain Against Terran

Even in the silver-to-gold tiers of the ladder, most Zerg's are used to starving out a Terran on two base in ZvT.  There's only so much army a Terran can produce on two bases, and crushing that one army can be a win-moment.  The fast third OC completely breaks this dynamic for the Zerg.

The question then is, even with an economic advantage, how do I manage a Terran with the resource to max 3 times over? Shawn ‘Sheth’ Simon, in an NASL ZvT, showed us shimmers of the answer against Choi Sung ‘Polt’ Hoon - the 3-base contain.

The 3-base ZvT contain works on this principle: If I retain an economic advantage, and both of us burn through resources at the same pace, I end the game with more money, and therefore more stuff. This is a long-term starve-out strategy.

A 3-base contain has three somewhat obvious objectives:

1. Prevent the Terran from getting a 4th base
2. Retain the eco advantage
3. Don’t die

The challenge lies in the managing the tactics to reach those objectives.  There are 2 Core Tasks and 3 Support Tasksnecessary.

Core Tasks

1. Mass expand
2. Army Trades

Support Tasks

1. Creep Spread
2.Burrowed Zerglings
3. Harrassment

We can use a chart to visualize what tasks are critically important for each objective.

Tasks	Objectives
	Prevent the 4th	Retain Eco Advantage	Don't Die
Mass Expand		x	x
Army Trades	x	x	x
Creep Spread	x	x	x
Burrowed Zerglings	x
Harrassment	x

Let’s see how each task contributes to meeting each objective.

Core Task 1: Mass expand

At in-game 15-minutes, notice the base count and position.

 “Retain the Eco Advantage” - Notice how far apart Sheth’s 4th and 5th bases are. A marine takes >45 seconds to travel that, making it nigh impossible for a single push to kill both. This means that when Sheth loses one, he’s still one base up on Polt.

“Don’t Die” - Once you’ve established an eco advantage, it costs you relatively little to continue expanding. With many distant bases, it means that Terran will need a lot of time to kill you, which continues to run down the clock.

Core Task 2: Army Trades

Let’s look at the large battles in the game.

	Start			End
Event	Time	T Food	Z Food	Time	T Food	Z Food
Battle 1	22:30	196	199	24:16	122	188
Battle 2	25:20	170	199	26:23	91	167
Polt Secures 4th	27:00	-	-	-	-	-
Battle 3	28:54	141	164	29:38	146	139
Battle 4	34:45	200	142	35:29	139	57

In this game, Sheth traded armies efficiently until Polt’s 4th base was up and running

“Prevent the 4th” - If Terran is starved, one option is a favorable engagement to break the contain, leaving just enough army to establish a 4th. Conversely, a cost-efficient full-army trade means both players reset, but Terran still has no 4th. Moreover, if he does take the central base, you may need an efficient army trade to collapse the 4th, which Sheth does in Battle 2.

“Retain Eco Advantage” - If Terran wants said favorable engagement, snapping off a medivac, cutting 10 food from his army, doesn’t help. Moreover, his defensive line is essential, while your 5th base is expendable. This greatly disincentivizes drop play. In fact, Polt didn’t start dropping until 25:30, when he felt confident that he would soon secure a 4th base. Finally, if Terran moves his whole army to assault your side bases, active army trades ensure your base costs him more than he’d like.

“Don’t Die” - Because Zerg replenishes army faster, Terran has no way to press in after such an army trade. More sands falls down the hourglass, but with the eco advantage, your hourglass still has more sand.

Support Task 1: Creep Spread

“Prevent the 4th” - Let’s look at Sheth’s creep spread

Center Base: Polt is ready to take his 4th at 15:20, but between Sheth’s active attention to creep, and Polt being busy trying to kill Sheth’s bases, the center base was not clear until 5 full minutes later.

Satellite Base: In parallel to this, Sheth spread creep on the satellite 4th base with an overlord, blocking this base as well. Because Polt was occupied, the creep wasn’t cleared until in-game 21minutes. This is a >5 minute delay of the 4th base.

“Retain the eco advantage” - As you know, creep accelerates the speed of your zerglings to run around and defend drops. Center-to-natural travel for zerglings is ~15 seconds off creep, but ~10 seconds on creep. 8 marines (stim + 2/2) deal >100DPS - saving 5 seconds saves >500 damage, which is 10 extra drones saved, or ⅓ of a hatchery.

“Don’t die” - A diligent terran recedes creep before advancing because of the tactical advantage from creep speed. This process takes a while. The eco-pressure from the contain may force terran to engage sooner than he wants, on creep, giving you more favorable engagements. Alternatively, they can choose not to fight until the creep is cleared, as did Polt, running down the clock for you.

Support Task 2: Burrowed Zerglings

“Prevent the 4th” -

Because of how busy Polt was, this burrowed zergling stayed there until in-game 27:00. Only then did Polt secure his 4th base - over 10 minutes late.

Support Task 3: Harassment

“Prevent the 4th” - Finally, at ~in-game 27:00, Polt finally secured his 4th base.

Sheth, after all this, lost the game. In a post-match interview, Sheth said, “I saw him get that fourth base and thought, well that shouldn’t be the end of me...and it was the end of me.”

If a satellite 4th is established, it must die, and a surgical strike is typically enough. Polt’s marines were positioned to fend off a zergling runby, but other options existed. Sheth had researched drop, and could have circumvented the marine position, eviscerating the fourth, and keeping the scales tipped in his favor.

Though Sheth went on to lose the game, he put up one heck of a fight the whole way, arguably leading for most of it.  Only because Polt endured the contain magnificently did he take the win.  Nonetheless, Sheth's execution, and candid admission of why he lost, demonstrates how to manage a 3-base contain.  With it, a 3-base Terran is far less terrifying.  

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