This mission will begin in an ethereal sand level, taking place right after the helicopter crash. Walker will be alone, trudging through a hellish sandstorm. Proceed forward across the bridge of sand. As you reach the other side of the bridge, Walker will be lectured by Konrad before snapping out of the vision. Adams will break you out of your trance. Lugo and Adams have been separated, but Adams awaits you by the smoking wreckage ahead.
As you approach it, you will hear enemies incoming. Run into the submerged ship ahead and vault over the side to the battlefield below. Use the concrete barriers as cover, and peek out to fire at the enemies to your left and in front of you. Adams will be downed as you approach, giving you a limited time to clear out the enemies and reach him. Use your desert eagle to take out the few enemies behind the barriers, and sprint up to help Adams out. He will need a minute to recover, so you will have to defend him from incoming enemies. Loot the ammo from the box directly to your right, and pick up the light mac hine gun while you're at it. A shotgunner will come up from the left, while a wave of lighter enemies will come up from the cover point on the right and the submerged ship bulkhead to your left. Watc h out for the enemies to the left especially, as they will not be visible to you until they round the ship's cabin, at which point they'll be practically right on top of you.
Note that you will be able to refill your ammo a second time via another ammo refill box behind the cover point to your left. A suitcase of grenades will be sitting all the way to the left side of this cover point. Use these ammo refills and the multiple cover points nearby to stay alive during the intense onslaught. Keep shifting your view back and forth from the left to the right and back again, as the enemies will come up from both sides in waves. If you get flanked by enemies on your left, your best bet may just be to charge them, knock them on the ground with a melee attack, and, once out of sight safely behind the ship's cabin so that you won't take any fire from incoming enemies on the right, execute the poor guys on the ground. If you find yourself running low on ammo as you fend the enemies off, loot guns from the corpses of any nearby fallen bad guys and keep on fighting. Adams will recover as the troops begin to dwindle.
Also around this time, a heavy soldier will come walking out from the middle of the opening in the blue ship ahead. He will be flanked by several regular enemies, so he might be a bit hard to see, but Adams or Walker will call him out when he gets out onto the sand. The lighter enemies will rush up to cover as the heavy slowly advances, trying to provide cover for him. Since they will be pressing hard towards your position, it can be difficult to prioritize the havy soldier as you properly should. If you have any grenades left from the crate, toss them out behind the cover points that the lighter soldiers are occupying in order to take multiple enemies out at once. When the heavy gets about halfway to your position, you should really start focusing on him; at this point, you should have eliminated most if not all of the smaller enemies so that you can take cover behind the left or right barrier and properly focus on blowing out the tiny visor in the heavy's helmet. He should fall just before he reaches you.
With the heavy gone, you should be cleared to push on ahead. Adams will recover with a smart mouthed quip about how poorly your mission has gone thus far. Be sure to grab whatever ammo you can from the fallen soldiers nearby, and search all the way to the right of the three barriers in the middle to find another ammo refill box. Head into the blue ship that the heavy emerged from when you are ready to proceed. Drop down to the lower level of the ship. Lugo will radio you, informing you that he has broken his arm in the aftermath of the crash, and that his weapon is nowehere to be found. Adams will report that the signal is coming from somewhere in the north. As you round the corner, you will be beset upon by numerous foot soldiers and a few snipers to boot.
Take cover behind the long metal barrier in front of the Alessia, the submerged blue ship ahead of you. A shotgunner will run up from the left side, so be sure to prioritize him when he gets up to you. Thin the herd with an automatic weapon as the soldiers charge you from the left side. When all seems quiet, slip over to the cover point on the left and grab some more sticky grenades. Vault over the cover point and zigzag between different cover points until you are midway up the battlefield. If you find yourself taking too much heat, remember that you can cause a giant sand cloud to erupt from the ground in this area by tossing a grenade out, a tactic that can be helpful when pinned down by snipers or enemies with automatic weapons. By the time you get around halfway up the battlefield, any additional entrenched enemies should reveal themselves. As you approach the ship ahead, don't be lulled into complacency by the relative silence. Three more enmies will rush out from the Alessia's left side as you approach it, and with their automatic weapons drawn squarely on you, they can be deadly if you aren't expecting them. Backpedal as they rush out, leveling your weapon at them and opening fire. They should fall as you reach the sand of the desert again.
With those three enemies dead, head forwards and to the right, into the door from which the enemies poured. A spiral staircase on the left will take you up to the next floor of the ship. Again, be careful as you ascend the staircase, as two enemies will rush you and engage you in close quarters combat. If you have a shotgun, definitely use that to clear out the stairs safely. If you are lacking a shotgun, simply backpedal down the steps and open fire with an automatic weapon to deal with them just the same as you did with the enemies who emerged from the ship downstairs. With the two enemies dead, ascend the stairs to find a crate of grenades behind the chest high wall on the aft of the ship, and a few weapons scattered about. Drop down from the hole in the ship's fence and take cover behind the small barrier ahead and to the right. You will have to face down even more enemies here, so be ready as you trudge out onto the sand once again.
The first group of enemies will hole up behind cover points ahead of you and to the left. Keep them suppressed until you get a chance to go in for a killing shot. Advance along the right side of the battlefield, as there will be more cover here. Enemies will begin to shoot out from the scar in the ship's hull to your right, so stay alert, as it can be difficult to see the muzzles of their guns poking through the hole in the hull until it's too late. Take them out and proceed up and to the right. Another enemy will try to pin you down from the left. Kill him off and take cover in his place. Another sniper will be on the ship ahead of you. Grab a rifle from behind the cover point and do a little bit of counter sniping. After killing the first sniper, another two will come out. Again, keep them suppressed until you can get a killing shot.
After killing the snipers, advance to the cover point diagonally ahead and to the right. You will find a crate of stun grenades waiting for you here. Keep pushing ahead and take cover behind the submerged ship ahead. More enmeis will come at you from the right. Use grenades to kill them off easily, or use an automatic heavy weapon like a light machine gun to mow them all down before they can even reach their pre-determined cover points. When all of the enemies have fallen, a veritable sea of weapons will lie at your feet discarded from the corpses. Take your pick of the many, many assault rifles and submachine guns currently at your disposal. You will be doing plenty of fighting against enemies with similar weapons, and you will be faced with plenty of extra ammo crates in the coming levels, so from this point on it's a bit easier than it has been before to pick your favorite weapon and just go with it for the remainder of the game. Grab a gun that you like, and proceed into the ship to the left.