When you enter the P'Jem System, you find that a group of Klingons are guarding the planet. The only way to access the planet is to fight them off.
Beam down to planet to find the surface covered in Klingons. Fight your way up the hill, defeating groups of Klingons along the way. Several useful ground combat equipment can be found here from weapons and kits to shields and armor. When you reach the top, you find out that the Vulcan ambassador you've been transporting is actually an Undine in disguise. After a quick battle, he escapes and you fight your way back down from the hill chasing him.
After being back aboard the ship, you detect an Undine ship approaching. You must defend yourself from the ship until Starfleet reinforcements arrive. The ship shoots powerful Bio-plasmic Warheads at you that can do serious hull damage. After Starfleet arrives, you destroy the ship.