Containment: keep them in their base

Lesson

13 of 14

Watch

A written lesson, no video

Practise

A checkpoint och a plan for your next game

A contain keeps your opponent in their base while you take the rest of the map. Done well, it wins slowly and cheaply: you spend a few units and a little attention, and they spend the game trying to get out. By the end of this lesson you will know when a contain pays, how many units it needs, where to put them, and how to break one when it is being done to you.

What you will learn

• What a contain buys you, and the one cost that decides whether it is worth it.
• Which units hold a contain in each matchup, and why they all share one property.
• How to size a contain against the width of the choke you are holding.
• How to expand behind it, and what to do the moment it breaks.
• How to break out of one, with a plan instead of a panic.

What a contain is

A contain is a line of units, usually at the mouth of your opponent's natural or main, that they cannot cross without losing a fight. It is not an attack. You are not trying to kill anything. You are trying to make every exit more expensive than staying home.

While they stay home, three things happen in your favour:

1. You get the map. Every expansion outside their base is yours to take.
2. Your scouting gets easy. A player stuck in one place can only do a few things, so you have fewer possibilities to rule out. This is lesson 7's idea: fewer reachable states means every look you take stays true for longer.
3. A stalemate is a win for you. Every minute nobody fights, you mine from more bases than they do.

The cost that decides it: reinforcement distance

Here is the price. Your new units are made at home and have to walk across the map to the contain. Theirs are made a few seconds from the fight. You have chosen to fight at the far end of your supply line against someone fighting at the near end of theirs.

So a contain is a trade: map control in exchange for reinforcement distance. Before you set one up, ask one question. If they break it right now, how long until my next group of units arrives? If the answer is "about as long as it takes them to walk to my third base", the contain is a bet that it never breaks.

Three ways to shorten that distance:

• Build a production building or two near the contain, or at an expansion on the way.
• Keep a second group halfway between home and the contain, not at home.
• Rally new units straight to the contain, not to your main.

The units that hold a contain

Every good contain unit has the same property: it does a lot of damage from a position it does not have to leave. It sets up, and the enemy has to walk into it. That is why a contain costs you few actions to keep and costs them many to break.

Check any of these numbers against upgrades in the Damage Lab.

By matchup, in broad strokes

• Terran against anything on the ground. Sieged tanks behind the choke, mines in front of them, a few marines or goliaths to spot and guard. This is the classic contain, because the tank's 12 range means the enemy has to cross a lot of ground under fire before it can shoot back.
• Zerg. Burrowed lurkers at the mouth of a ramp, with zerglings nearby to punish anything that runs past. Lurkers need detection to kill, so the first question for your opponent is whether they have it.
• Protoss. Harder. Protoss units are expensive and strong, and a strong unit standing still is a strong unit not attacking. Reavers and a few cannons can hold a spot, but most Protoss players get more from pressure than from a standing contain.

And the counters to know: air units ignore a ground contain completely, and a drop behind it makes the whole line pointless. A contain against a player with transports or a flying army is not a contain.

How many units a contain needs

This is lesson 4 applied. A choke limits how many of their units can shoot at once. If only four of their units can fit through the gap side by side, then your contain only has to beat four units at a time, not their whole army.

So size the contain to the choke, not to their army:

• A narrow ramp. Two or three sieged tanks and a mine field hold it against a much bigger ground army, because the attackers arrive in a column and the front of the column dies first.
• A wide choke. You need enough to cover the full width, or they flood through the side you did not cover. Tanks spread in a shallow arc cover width far better than tanks in a clump.
• An open area. Do not contain there. With no choke, their whole army fights at once and your contain is just a smaller army in a bad place.

The shape matters as much as the count. Units in an arc around the exit can all fire at the same spot. Units in a line along the exit mostly cannot. See it in the Flux Lab: put the same six units in a line and in an arc and count how many are in range of the choke.

Expanding behind a contain

The contain is not the goal. The bases it lets you take are the goal. The order is:

1. Set the contain.
2. Take the next expansion straight away. The whole point is income they do not have.
3. Keep the contain the same size or smaller while your economy grows. Spend the new income on production, not on thickening the line.
4. Check the line every twenty to thirty seconds. A contain dies from being forgotten more often than from being attacked.

When it breaks

It will break eventually. Plan for it:

• Pull back, do not trade. Tanks unsieging under fire die. If the break is coming, unsiege the back tanks first and leapfrog out.
• Fall back to your expansion. Your spread out bases are now the weak point. Every unit should go to the most valuable one, not stand where the contain was.
• Look for the counter attack. A player who just broke out has sent their army to your side of the map. Their base is now the empty one.

Breaking out of a contain

When you are the one being held:

1. Do not walk into it piece by piece. Five units running in one at a time die one at a time. Build up, then go together.
2. Hit it from two sides. Drop or run a group around behind while the main army pushes the front. A contain is built to face one way.
3. Bring what it cannot shoot. Air against a ground contain. Detection against lurkers. Fast units that run past to hit their expansion, which forces them to pull units off the line.
4. Or ignore it. If you have transports, you do not need the front door. Expand by air, or drop their main.

Common mistakes

• Containing with an army that should be attacking. If you are ahead enough to hold a contain, check whether you are ahead enough to just win.
• Forgetting reinforcement distance. Your rally point is still your main, and the contain gets broken while your units are halfway across the map.
• Thickening the line instead of expanding. Every extra tank at the contain is one you did not spend on production or a new base.
• Clumping. A tight clump covers a narrow slice of the choke and invites splash. Spread along an arc.
• Containing a player who can fly. Check for air tech and transports before you commit.

Practise

• Drill 1: the arc

  In the Flux Lab, hold a choke with six units. Try a line, a clump and an arc, and note how many can fire at the exit each time.

• Drill 2: the fight at the exit

  In the Battle Lab, run three sieged tanks against twelve hydralisks, then against twelve zealots. See which contain holds and why.

• Drill 3: the walk

  In a practice game, time how long a new unit takes to walk from your production to the enemy natural. That is your reinforcement distance. Remember the number.

• Drill 4: the ledger

  Pick any plan you use every game. Write what it gives you and what it costs you, then test it in all three matchups. Keep it only if it still pays.

Checkpoint