The composition of Zergling, Baneling, and Hydralisk has shot up in popularity in the TvZ match up. There are some signs that Terran have been adapting to this new style.

Background

Zergling, Baneling, and Hydralisk (ZBH) are common for ZvP, but it has never really been a mainstream thing in TvZ until recently. As far as I can remember, Solar was the first notable player who had used this composition in TvZ last year, but it did not really kick off. I had also seen him using it earlier this year, but again, other Zergs were not using it. However, ZBH has gained lots of traction in the past two months, and it has become one of the few mainstream mid game styles. This style has also been used on ladder by casual players, and it has received much attention on forums this week (here and here). The current mainstream main styles are:

• Zergling and Baneling (quick Hive)
• Zergling, Baneling, and Mutalisk
• Zergling, Baneling, and Corruptor
• Zergling, Baneling, Roach, and Ravager (sort of replaced by ZBH)
• Roach, Ravager, and Infestor
• Zergling, Baneling, and Hydralisk

Hydralisk’s value comparison

Zergling, Baneling, Roach, and Ravager do not consist of units that can attack air, and that could be an issue against multi-pronged drops. Terran will gain value from these small hit-and-run skirmishes, and make a strong push with +2/+2 after that. Similarly, Zergling and Baneling with quick Hive also do not have anti-air, and it has become less popular now than when Queen’s range was just buffed. The addition of Hydralisk clearly improves Terran’s drop heavy mid game.

Then, why is Hydralisk more popular than Corruptor and Mutalisk? Mutalisk provides the best map control, but it is very bad in big battle. Mutalisk also is a good option for harassment as we have seen that in Wings of Liberty and Heart of the Swarm, but players are actually getting a lot more efficient with just Zergling harassment now. Further, Mutalisk does not transition to Hive tech as well as other composition, and it is a major consideration in Legacy of the Void. Thus, Mutalisk has become an inferior option as of current understanding.

The Zergling, Baneling, and Corruptor composition was popularised by Dark in late Heart of the Swarm, and it was simply a direct replacement for Mutalisk. Corruptor is easier to control and requires less attention than Mutalisk, and more importantly, its high health makes it a superior choice in big battle. You can essentially A-move the group of Corruptors forward when you want to engage, and focus on managing the land units in the battle. It is in Zerg’s favor if Widow Mines target the Corruptors instead of the ground units.

Hydralisk is stronger than Corruptor and Mutalisk in battle, and it provides the anti-air utility that Roach and Ravager cannot provide. The other benefit of Hydralisk is its effectiveness in smaller groups, and this quality is evident when Zerg split their units to defend multiple locations. You cannot really split up your group of Mutalisks, and Corruptor is restricted by its relatively slow movement speed. The one advantage Corruptor and Mutalisk have over Hydralisk is upgrade. Both Missile Attacks upgrade and Melee Attacks upgrade are done in the Evolution Chamber, so you have to make a choice between upgrading your Zergling and Baneling or Hydralisk (unless you make more Evolution Chamber). The Flyer Attacker upgrade for Corruptor and Mutalisk is in the Spire, so you can research upgrade for all the units at the same time. This is something that Zerg players have addressed, and I will discuss it below.

Play style

Zerg usually play a defensive style in the match up, and this overarching “offender versus defender role” foundation does not shift with ZBH. The two vods below show how ZBH games generally look like. There is no drastic change to the overall play style.

The default game plan for Terran is to use the mobility of bio and Medivac to harass Zerg and control creep. Then, when +2/+2 upgrade is completed, Terran gather the units for a frontal push. Of course, at the same time, there is a drop on the other side of the map continue to do what it does. ZBH shines in defending the drop attacks early, and the +2/+2 push. Thus, based on the current Terran play style, ZBH is arguably the best mid game composition as of current understanding.

The role of ZBH is to allow Zerg to be as cost efficient as possible in the defensive mid game phase, and transition out to Hive tech. The upgrade choices are in line with this goal, such that only level one Missile Attack is upgraded. Zerg either start off with Missile Attack and Carapace +1/+1 then go back to Melee Attack and Carapace +1/+2, or start off with Melee Attack and Carapace +1/+1 then squeeze in level one Missile Attack before going back level two Melee Attack. No matter which path Zerg take, they still converge back to level two Carapace, level one Missile Attack, and level one Melee Attack in the mid game. This set up has been working well for Zerg. The three production screen shot images below were taken from the same game. The first one shows a normal Melee +1/+1 upgrade, the second one shows a switch to Missile Attack upgrade while Carapace continues to level up, and then the third one shows Zerg go back to Melee upgrade. In the vod below, Zerg did not get level one Missile Attack, and the trade just did not go well.

Once Zerg have reached the Hive tech production, Hydralisk is no longer produced. The transition happens when Ultralisks are in production. Spire will then be added for Corruptor, Viper, and Broodlord. This explains the rationale behind having only level one Missile Attack upgrade, and this again shows Hydralisk is only used as a mid game unit to bridge the Hive tech.

Terran reaction

There is this fundamental understanding in TvZ that Terran need to have aoe support with bio against Zerg. Siege Tank was the only choice in Wings of Liberty, and Widow Mine and Hellbat were later added in Heart of the Swarm. The general consensus is to use Widow Mine against Zergling and Baneling, and use Siege Tank against Roach, Ravager, and Hydralisk. Thus, it seems awkward to pick between Widow Mine and Siege Tank against ZBH.

Like many others, my intuition is to use Siege Tank. Widow Mine is not effective against Hydralisk, and Siege Tank is ok-ish against Zergling and Baneling. Interestingly, in the post game interview below, Maru explicitly stated that Widow Mine works better than Siege Tank against ZBH.

Ironically, Maru used mass Siege Tank against Solar (see vod below), so I am not exactly sure what his perspective is on ZBH. It is plausible that he used Siege Tank defensively on Frost against Solar, because it is a good map for a Hydralisk timing due to the wide area to form an arc. It would be extremely hard for Terran to hold against that with Widow Mine instead of Siege Tank. However, it is difficult to get value out of the Siege Tank when Terran have a hard time pushing across the map diagonally.

I have seen both Widow Mine and Siege Tank being used by other Terran players, and it is difficult to suggest which is a better choice based on the games played recently. However, given the fact that Terran players who are producing Widow Mines with a Reactor Factory, lift the Factory for a Tech Lab to produce Siege Tanks implies the preferred tech path is probably Siege Tank.

My approach is to get a second Factory before the sixth to eighth. That means, after you have reached the 5-1-1 convergent point, you put down another Factory for a 5-2-1 and produce two Siege Tanks at a time. This then lines up with the +2/+2 bio upgrade and +1 Vehicle Weapons upgrade timing attack. Therefore, you make a Siege Tank heavy attack in the mid game (see image below). aLive actually did just that yesterday against Solar in SSL, but the execution was not on point though (see first vod below). INnoVation had also shown the similar approach in VSL recently (see second vod below).

The other thing that Terran can do against ZBH is to commit more heavily to drop. While ZBH has decent mobility in defending the multiple bases, Hydralisk is not as fast as Zergling and Baneling. Thus, the Zergling and Baneling have to wait for the Hydralisk before they can engage the drop. This is not exactly an issue against a typical TvZ mid game drop, whereby there is only one or two Medivac of units. Generally, Terran do not drop with more than two Medivac in TvZ, because you do not need too many units to serve the purpose of drawing Zerg’s attention away from your main force. However, it becomes problematic when the drop is consisted of three to four Medivac of units, because Zerg have to wait for the Hydralisk before engaging. The three to four Medivacs of +2/+2 bio will trade well against the +1/+2 Zergling and Baneling. Terran can deal good damage with that force of bio before the Hydralisks arrive. Further, Terran can just load up and run away to avoid battle with the Hydralisks when they join up with the Zergling and Baneling, and Zerg cannot punish Terran for that without Mutalisk or Corruptor.

Other thought

It is relatively easy to plan the Siege Tank attack when you know Zerg are going for ZBH by default in the current metagame. However, it is not that effective against other composition, so I expect Zerg to mix builds around more in the future. From the Terran’s perspective, it is difficult to know what mid game composition Zerg choose when all you see are Zerglings and Banelings early in the mid game.

The other interesting observation is how Zerg attempt to fit a second tech to ZBH. Some tried Infestor, while others tried Lurker. The results so far suggest it is better for Zerg to simply stick to just ZBH and tech up quickly. Below are some examples of second tech.

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