+1 deployment bonus (20 maximum).
"Knowledge of the terrain is the key to victory!"
Comments
By default 4 troopers are deployed at one time, if all 4 troopers are wiped out then the next 4 arrive. Certain skills can change this number, even skills of the enemy. The scout skill increases the deployment number by 1. Two skills that can lower the other players deployment number are 
Reverse Attack and 
Spy .
For example, if you had 2 scouts waiting to come into the battlefield then you would have 6 troopers deploying at one time... 4 (default) + 2 (scouts skill x2) = 6 troopers deploy.
...but if your option used Reverse Attack then this is back down to 4.
4 (default) + 2 (scouts) - 2 (enemy Reverse Attack) = 4 troopers deploy.
The two strategies are 'divide and conquer' versus 'swarm attack', both strategies are highly debatable when conceding area damage (grenades etc).