You witnessed a landing operation of the enemy. Every second, it resets the new force. The only chance to survive - is to sit behind the turret and begin to methodically destroy the enemy. Marines are extremely vulnerable in the sky, but if you give them the opportunity to disembark and go into a dense, they become extremely dangerous, they can only clear the grenades. When it becomes very difficult and the enemy will apply heavy equipment necessary to use the rocket launcher, they can cope with any adversary.