The first part of the challenge is to defend the base from 8 waves of zerglings, totaling 22 zerglings,
Build a barracks to the bottom right of the supply depot, then a bunker between the barracks and the vespene geyser. The first zealot will attack the supply depot. Do not garrison the bunker until four marines are trained; the zealots will attack the bunker instead once it is garrisoned. Build a refinery and supply depot to extend the wall on that side of the base.
On the other side of the base, build another bunker and a barracks with a tech lab. Again, do not garrison the bunker until it can be filled at once. Extend the wall around the northern side of the base if necessary.
Alternatively, position an SCV directly in the position of the warp gates BEFORE they are warped in, this will prevent the probe building the warp gate. When the first zealots warp in, run it around with the SCV down towards the bottom of the map, no need to go down the ramp, by this time the player should have a bunker + troops in, just bring it back, and dispatch it. just keep expanding from there, since the probes never attempt to re-build the warp gates. The player will have only 1-2 gates left to deal with.
Score the rank of Gold in the “Rush Defense” challenge mission.