The players start down the bottom of the rig. Some choice of weapons will lay in front of them. The only way to go is up the staircase. The first room of hostages will lie in front with two possible doors to breach. After this room has been cleared you must fight your way up the oil rig to the second room of hostages. The mission will finish after this room is cleared. You are not allowed to kill any hostages.
There are large number of enemies in this op: (at least 92 on Veteran). They come in waves, triggered by your progress.
Wave 1: Triggered by successful breach of first room. On Veteran, about 16 enemies. They come in sub-waves: the first is large (about 10) and the rest in groups of 3 or so aggressively advance on you.
Wave 2: Triggered by reaching the top of the stairs to the second level. Aggressively advance on you. Sometimes they come down to level one before you reach the stairs.
Wave 3: Triggered by advancing along the second level deck toward the target at the far end of the deck. Some enemies are already on deck, others rappel down. Aggressively advance on you.Note: A chopper also appears. Shoot it down ASAP! Use an AT4, RPG, or a Stinger. You can also use the grenade launcher attached to the M4A1 you spawned with.
Wave 4: Triggered by advancing along the second level deck toward the second objecting (at the far end of the deck). They mainly snipe and keep their distance, but will advance slowly upon you.
Wave 5: Triggered by reaching the target at the far end of the deck and advancing toward the next target. Aggressively advance upon you.
Wave 6: Triggered by going around the corner of the far end of the deck from the second objective (past the stairs).
Wave 7: Triggered by reaching the top of the stairs to the third deck. Aggressively advance on you.
In addition to the final wave who advance aggressively on you once you reach Level 3, there are snipers on a balcony; and also enemies who remain in-place until you advance into their line of sight. These enemies are in the far left corridor and the one next to it so make sure you take them out first.