The standard safe TvP mech opening. Build a factory before expanding, produce a siege tank, then take your natural expansion behind the tank's defensive cover. The siege tank at your natural choke eliminates the risk of zealot run-bys that punish faster expand builds.

The key timing is getting siege mode researched before the first zealot pressure arrives. Position the tank to cover both the natural ramp and the expansion building. Add a second factory and machine shop once the expansion is running, then transition into a full mech composition of vulture, tank, and goliath.

Siege Expand works on nearly any map and is the go-to choice when you are unsure what Protoss is doing. It is strongest on maps with tight naturals where a single tank covers the choke. Weak against early zealot pressure if the tank or siege mode research is delayed, and can fall behind economically against a Protoss who expands faster without punishment.