This is a hit-or-miss strategy that will either work very well or not at all. Place all of your soldiers along the east wall, preferably with one in front of the door. If you are lucky, there will be no immediate threat in the east wing and few aliens attacking from the outside. When your turn starts, go directly into the corridor with the stairs, ignoring any aliens in the east wing. Take out any aliens on the staircase and move all of your troops into the corridor.