This Build Order is a classic response to a Protoss Fast-Expand (Nexus 15 or Forge Expo). This is THE most used build against the Protoss and you will need to master it. Taking your three bases will slow down taking gas and producing units because you will have to produce a huge amount of Drones to stay at least at the same economic level as your Protoss opponent because you will capitalise on the delay of your opponent's Warpgate. Obviously if you discover that your opponent is opening the game with a One-Base strategy then it is important not to place your B3 without taking gas to be safer.
A Probe that blocks your B2 will necessarily slow down your Build, but you can avoid being "TOO" late!
- You can attack the Probe with your Drone and try to place your Hatchery anyway.
- While attacking the Probe with your first Drone, you can take your B3 with another Drone (Your B2 will be the replacement for the B3).