Hello. If you decided to read my guide, you probably want to find out what the secrets on the "Onslaught" map are or you want to remember / check what they are.
This map is the first map of the campaign. It is about surviving until backup arrives.

Secrets are simply places on the maps that are not immediately available / visible (you need to enter e.g. a wall or shoot at that spot).
Have a nice reading.

You have to shoot into this black wall.

In addition, it is worth underlining that additional (random) items appear on the map in certain places.

S - Secret

Polish version
List of my SAS guides
Thanks for reading!