TvT: Revisiting the Relative Role of Offender versus Defender

Two years ago, I wrote an article about the relative role of offender versus defender focusing on understanding on the early game dynamics. The current metagame in Legacy of the Void brings a new perspective to this topic.

If you have not read that article, it would be better that you read that before you continue.

Also, many have asked me why I use “offender versus defender”, and not “attacker versus defender” or “aggressor versus defender”, after I had put forward this concept. No, it is not an Australian thing. It just happened that I picked up basketball in 2015, and the term used in the game is “offence versus defence”. I simply bring it over incidentally, and I think it may be better for me to keep it that way for consistency.

The concept of offender versus defender

First and foremost, I want to be clear that I did not create the concept itself, but I simply provide a systematic explanation based on observation from countless number of games. Also, I am not saying I am the first to observe it, but it just happens that my posts on this topic have been picked up and accepted by many. You may have been applying the concept in your game without noticing it anyway.

Players usually have pre-determined roles in a match up during a specific time frame, such that one player is the “offender” and the other is the “defender”. For example, in Terran versus Zerg, Terran is the offender while Zerg is usually the defender in the mid game. These “roles” define how both sides play the game.

The concept of relative roles in a match up is so embedded in players’ mind that it is difficult to adjust the play style accordingly. A great example is how Terran players kept falling into the trap of being the offender against Adept Phoenix at its peak. Players are so used to the paradigm that Terran is the offender and Protoss is the defender in the match up that Terran keep attacking in the mid game when they should not have.

Then, who is the offender or defender in a mirror match up when there is no pre-determined roles? More specifically for this article, what decide the relative roles in the Terran mirror? While it is intuitively convenient to suggest that the builds used decide the relative roles, there is more depth to it. What happens when both players use the same build? Thus, although it is not wrong to say builds used is a factor, it is the implications based on the build order that really decide the relative roles.

The best way to know the relative roles is to identify which player has the “priority to deal damage”, and this is determined by who has the earlier timing and has the potential to deal more damage. Importantly, the timing and the potential factors are so intertwined that it is difficult to disintegrate them. Let’s use a proxy multiple Barracks Reaper build versus a Cloak Banshee build as an example. Both are aimed to attack rather than to defend in the early game, but proxy multiple Barracks Reaper hits earlier and has a greater potential to deal more damage. Thus, the proxy multiple Barracks Reaper player has the priority to be the offender, and the Cloak Banshee player has to make adjustments to be the defender. If the Cloak Banshee player does not make the necessary adjustments, s/he will have lost the game before the first Banshee can be produced. Many players would then say, “well, it is just a lost due to build order, and my opponent’s counters mine”. However, the defeat can clearly be attributed to the lack of understanding of the concept of relative roles.

More often than not, players find themselves playing against less extreme builds than proxy multiple Barracks Reaper, and it is difficult to determine the relative roles based on the abstract criteria I mentioned above. Therefore, in the article I had written previously, I used the relative timing of the Starport as the rule of thumb criteria to identify the relative roles for macro builds.

Timing of Starport

The relative timing of Starport is a good criteria, because the attack usually involves the first unit produced from the Starport. Then, logically, the timing of the attack is depended by the timing of the Starport, and this is particularly influential when the match up is so 1-1-1 oriented. For example, the timing of a drop planned by the build order is determined by how early the Medivac is out, which is determined by how early the Starport is placed down.

Let say, both players go for a Cloaked Banshee build, but one uses a 15/16 Reaper expand opening while the other uses a double gas opening. Clearly, the latter build has an earlier Starport, and hence, the Banshee will hit earlier. This essentially means that the latter player has the priority to be the offender, and the former player has to make adjustments to be the defender. If both players continue to execute their builds as planned, the earlier Banshee would pile up damage a lot earlier and quicker. By the time the Reaper expand player has his or her own Banshee at opponent’s base, s/he would have easily lost enough workers that the game has already ended. Further, the player with an earlier Banshee could prepare by making a Raven after the first Banshee to prepare for the opponent’s Banshee, so the player with the earlier Starport will win the game if both sides continue blindly with their build orders. The Reaper expand player has to adjust by not trying to match opponent’s Banshee with his or her own, but focus on defending the Banshee first as opponent has the priority to be the offender. For instance, make a Raven instead of Banshee, or a Viking with Missile Turrets.

What happens when both sides use the exact same build with the same Starport timing? No one has the priority, and both can choose to be the offender.

The Cyclone factor

The underlying reason behind the timing of Starport being an important criteria is its alignment with almost every aggressive build’s attack timing. However, the introduction of Cyclone in Legacy of the Void has changed that, as Cyclone is arguably the most defining unit in the early game of the mirror match up. It is so crucial that some common builds even delay Starport in favor of Cyclone. Adjustments have to be made to account for the timing when the opponent attack with Reapers and Cyclone, and the Starport plays a smaller role in that. That means, players need to scout opponent’s build to know whether that build has the potential to execute a Cyclone timing, and this is a consideration on top of the relative timing of Starport when a player is figuring out who is the offender.

Two of the most common macro openings in TvT are the 15/16 Reaper expand and the double Refinery double Reaper. Generally, the investment in tech to delay expansion with the double Refinery opening (at 15 and 17 supply) allows the player to make an earlier Cyclone and/or an earlier Starport, so s/he has the priority to be the offender. The build has a timing with two Reaper and a Cyclone, which requires the opponent to adapt accordingly. This build has the option to have a Banshee follow up, and again, it puts the opponent in the defender position.

Early to mid game transition

Thus far, I have emphasized on how build interactions affect the relative roles and it is less of a player’s preference (of course, you can have a preference in build for that matter), but the priority to be the offender in the early to mid game transition is more of a player preference that is less related to the builds used.

Let’s continue using the above two common macro builds in the metagame as the example. While the double Refinery opening has the priority in the early game phrase over the Reaper expand opening, both builds converge to have 1-1-1 and two Command Centres at about the same time. That means, unless one side has taken a momentum swing in the early game, the priority in the relative roles is not determined beyond the early game. If these two different openings converge to this transition phase at about the same time, then two players using the similar openings should also show the same transition phase. In this transition phase, both players will put down two more Barracks (you can also favour an earlier third Command Centre instead) and research Stim to converge to a Marine, Tank, and Medivac army. There are two main ways in terms of army composition in this transition period: one is to focus on the army strength in the present to take the role of the offender, and the other is to focus on the army strength in the mid game by being the defender.

The two vods above are GSL games betwen GuMiho and TY, and I timestamped both at the time when both were having their Factories under construction. It is evident that GuMiho prefer to be the offender, while TY prefer to be the defender in the transition period. In the first vod, GuMiho had successfully delayed the Command Centre at the natural, so one may argue that TY simply got forced to give the priority to GuMiho. However, in the second vod, neither player really had interrupted the opponent enough to earn the priority to be the offender, so that shows a clearer picture of their respective preference. The reason I said GuMiho is the offender and TY is the defender is that GuMiho continues to make multiple Cyclones in the transition period, while TY puts down a Tech Lab on the Factory rather early for Siege Tank production.

The pressure is on the player who chose to be the offender during this period to deal damage to compensate the lower Tank count in the beginning of the mid game. One important point to note is that the Cyclone count also allows the offender to have map control over the defender. In my opinion, the choice of the relative role during the transition period should also be based on the map. It is easier to defend on maps with a ramp at the natural, as the offender’s Cyclones would have a harder time to maximise the output.

The role would quickly swap over if the offender in the transition period does not pile up enough pressure. Once the defender has gathered a decent number of Siege Tank, s/he has the priority to be the offender by pushing out. In general, Cyclone’s value diminishes as time goes by, and hence, you never see players continue making Cyclone in the mid game. Thus, the player, who has been producing Cyclone and has a lower Tank count, has to defend against the attack of the other player who has a higher Tank count. Moreover, it is normal for the defender in the transition period to make Vikings and Raven for their defensive capability, and this smoothly set up a nice Tank push with air control. This is something that I have discussed in an earlier article.

Arguably, the only way to do that is to prevent or delay the attacking player from gaining a good attacking position with the Siege Tank in siege mode, and this mean s/he has to force a battle when the opponent is moving across the map with the Siege Tank. This does not only delay the push to allow your own Tanks to set up in good defensive locations, it also gets the best value out of the Cyclones before their value really takes a big dip. I timestamped the vod below at the point when TY pushes out after he had several Siege Tanks, and GuMiho had not really made the Tank transition. GuMiho engaged TY’s army in the middle of the map, and he got destroyed. The commentators were critical about the engagement, but the decision was actually spot on in my opinion. The only thing you could argue against GuMiho was the execution itself, but it was still reasonable given the circumstances. The Cyclones were low in health and GuMiho wanted to repair them, but TY did not give him much time to do so. GuMiho then placed his other units in the bush to buy time, and that was as good as it could be. However, the main issue was when TY siege up all Tanks, and GuMiho attacked into that position. The outcome could be different if the engagement was done when TY’s Tanks were not siege.

I timestamped the time when TY did a similar push in the other game in the vod below. GuMiho’s decision was the same, and that was to delay the push as much as possible with the Cyclones he had.


The concept of relative roles in TvT is critical in the early game and transition period to the mid game. Previously in Heart of the Swarm, the main factor that decides who has the priority in the relative roles is the timing of the Starport. However, Cyclone has changed that by becoming another important factor for the relative roles, and more interestingly, it gives players the choice to be the offender by being selective in the production investment in the transition period.


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