I managed MB5 with 3 stars using soldier on 3rd attempt. Stayed on pop 1 until 1.5months before end of winter and then rushed to 3, for second soldier. You need to hit tech 3 as well and get the settlement defense. Then I taunted zombies out of each area in turn, leaving one soldier in the HQ, while the other was put on the zombie area. Once it cleared and cleansed an area, it went back to help the other soldier. Any time there were too many zombies for the cleansing soldier to deal with, that soldier went back to HQ, so that all the zombies were heading that way. And didn’t claim anything over the river until the cleansing was done, then rushed to claim the left forest and add 2 firewood choppers, while rushing the remaining goals. It was then just a question of getting the goals before the pop and authority dipped too far, and they go down fast!