Kilroy was Here Achievement
Kilroy was Here10
Make it through the tower to the winch room without being spottedDuring Mission 6, 'Tiergarten Flak Tower', you will receive an objective to find a path to the roof of the flak tower. Upon entering the tower, you cannot be spotted at all. Following the video below, stay crouched most of the time and only eliminate enemies in your path.
Once you reach the roof, there will be sound masking but still be careful as there are guards patrolling. Work your way across the roof and up and down stairs until you reach the winch room. After a short cutscene, the achievement will unlock.
Guards can become aware if anything is amiss (like finding a body), but if you are spotted at any time, just reload the checkpoint.
Thanks to 360GameTV for the video: