Similar game I took part in a few years ago in the Poconos. A "castle" defended by about 10 people, and about 30 people (including myself) attacking.
The building was a two story, simple wodden fortress type thing with ramparts and towers, etc.
We split the 30 or so attackers into three groups. Center group providing suppressive fire while the other two groups flanked left and right. Once the flankers were in position to draw defenders away from the front wall, the center group attacked.
Once the center group began moving forward, the two flanking groups converged.
Surprisingly enough, even though the damn things hurt, we had alot of ex and current military guys with us and no one backed down to to stop and shoot- we all ran the whole way.
All 30 players were shot, most multiple times, and the building was not taken. The defenders lost one as the result of a lucky shot during the first few seconds.
I took 4 hits - 2 to the torso and 2 to the head - one in the goggles and one splashed right through the breathing grate and let me tell you how ****ty paintballs taste.
Had we been doing this for real, we would have counted 30 KIA's in a little over 2 minutes and I wouldnt have a face. Hopefully the guys in Iraq know a little more about building assault than a bunch of college kids.