Terran Counter to Arbiter Play
This article discusses possible counters to Protoss Arbiter Late Game Play. For the article about performing this opening build see Late Game Arbiters
If Protoss is playing very defensively or fails to take a third base at normal timing, it is likely that Protoss is either going Carriers or Arbiters. It is crucial to use Comsat Scan to find out which tech tree Protoss is going.
Another possiblity is luring the Protoss' base defense out and sneaking a Vulture in to scout and harass, or using a Vulture/Tank drop to scout and harass.
One Stargate Arbiters
If Protoss builds one Stargate it is likely that fast Recall will be used. Recall can be deadly for Terran if the Terran is not prepared. However, if the Terran is prepared it can make for an easy win.
After scouting one Stargate, Terran should immediately line the perimeter of the main and natural expansion with Turrets. Each Turret should be surrounded by Mines to avoid Recall on the perimeter. Mines should also be placed in the inner area of the Main near the Factories and the Command Center to prepare for a Recall that gets all the way inside the base. A few Tanks and Vultures, along with Mines and Turrets, should easily hold off the Recall while the rest of the Terran army protects the main front.
Terran should play defensively until the Recall occurs unless Protoss starts aggressively expanding. Once the Recall occurs, a counter attack should be able to end the game. If Protoss aggressively expands, Terran should either counter expand and build Mine/Turret defense at each expansion, or Terran should attack Protoss right before the expansions start to payoff.
Two Stargate Arbiters
If Terran scouts Two Stargate Arbiters, it is likely that Protoss will try a full attack with Stasis, although Recall is likely soon thereafter.
Terran should immediately build a Starport, Science Facility, research EMP, and build 2-3 Science Vessels. It is very important for Terran to wait for 2-3 Science Vessels with EMP before attacking Protoss, otherwise Stasis is likely to make a large portion of Terran's army useless.
Once Science Vessels are in play, it is very important to scout ahead of one's army with both 1-2 Vultures and Comsat Scan. If Terran does not know where the Arbiters are then Terran is likely at a large disadvantage. Once the Arbiters are found on the battlefield, one must attempt to EMP them before engaging in battle with the Protoss army. EMP is very deadly and can both nullify the Arbiters' stasis and eliminate the Plasma Shields of the Protoss army. Thus, it is important to take the time, using proper scouting techniques, to EMP the Arbiters.
When after scouting One or Two Stargate Arbiters it is important to build 2-3 Goliaths to kill Observers. If the Protoss has information about where Terran Science Vessels and/or army are located, then it is easy to either Recall in Terran's base once Terran pushes out, or Stasis Science Vessels before they can EMP. Thus, Goliaths serve the dual purpose of both being able to attack Arbiters and making them less effective due to killing Observers.
Using recall to your advantage
While recalls are unwanted events, one can use the situation to one's advantage. In TvP, it is crucial to keep one's army together. In the case of a recall, the Protoss's army becomes significantly weaker, thus providing the Terran army an opening to overpower the Protoss army. One should evaluate the situation. If the Protoss threatens a crucial element of the Terran's base (armories or taking down the main) it should be more advisable to deal with the recall first. However should the Protoss recall prove to be little threat, one can seize the opportunity to attack Protoss's army head on. Due to a Terran's often crowded base, it is easy to hold off the recall with few tanks and vultures due to the simcity. Taking advantage of this situation, the Terran can first overpower the Protoss army, establish a desirable forward position, and hold off the recall with minimal casualties and by using units produced from factories.