Barracks Barracks Supply (vs. Zerg)
The Barracks Barracks Supply build, also called BBS, consists of building two Barracks before a Supply Depot is made. Because it is very difficult to transition out of BBS it is considered an all-in build. It is capable of being used in any match-up, but it is most successful when the opponent either Fast Expands or Techs quickly. In many instances it is used as a surprise tactic, and is often utilized as a proxy to maximize the killing blow.
The efficacy of BBS in this match-up is strongest due to the common instance of 12 hatchery as being the staple in ZvT. Bunker rushing may follow the initial rush of Marines and SCVs, and can quickly end the game from that point on. If the Zerg opened with a fast Pool variant however, a Terran must retreat and proceed to either FE or tech. If the Terran had made proxy too far from the main he has no choice but to all-in the Zerg, as he would be unable to defend his main and produce a constant stream of Marines to handle both locations.