spoiler (click to show/hide)
Tombstone/your squad initially goes to China to find out why Russia is working with China. Cue intro in Ocean/Fishing in Baku, commander of squad dies. Your battleship commander promotes you to commander. Commands you/squad to go to China to save a "VIP," and "his wife." Blah blah blah, sneak in. Fight Chinese with help of CIA agent you won't see again as VIP/Wife and him exit on helicopter toward Battleship.
China is pissed and says the US invaded or something (never really explained) EMP is hit. US Battleships in the Indian(?) Ocean are hit and crippled.
China goes to war with the US saying the US killed VIP. Tombstone/squad goes to a crippled Battleship to retrieve intel/HD from battleship before China can get it. Cue sad music as refugees from previous level (which says there's 300,000 on the ships but you only see like... 8 in the entire game) as you guys leave because Irish wants to save people flee China with ya'll, but anyway refugees are trapped and going to drown like some Marines trapped underwater as well. Some other CIA dude (or the same, forgetting) that is in charge of your squad for this level says leave them which pisses Irish off.
Blah blah blah, China attacking warships, never anything about back at home.
Blah blah, stuff to do. You are put in charge again and "Hanna"/VIP's "wife" joins squad to protect him, help you in China to bomb an airbase.
Go through Hurricane/Typhoon, whatever you call it. Very pretty, very much like a tropical storm. Bomb airbase. Get caught in blast, Chinese capture you PLOT TWIST Hannah is working with the Chinese. "Pac" is mysteriously gone, assumed dead.
Blah blah blah, prison. Blah blah blah, HEY BATTLEFIELD 3 REFERENCE WITH DIMA FROM THE SEINE/FRANCE ASSAULT IS BACK! Break out of prison with Dima to find Hannah who Irish is reasonably pissed at. Find out Hannah did it to... whatever... cover? I dunno, the reason is barely there and flimsy.
Escape with Hanna. The tram ya'll are riding down the mountain is powered down and shot down. Dima dies, thereby cutting BF3 character out. Ya'll three (Hannah, Irish, yourself) are in the mountain for days with barely anything to eat or drink. Somehow regroup with a group of marines and a potty-mouth that doesn't like others potty-mouthing her female commander after fighting through Russians to get to her, thereby proving the intel initial Tombstone squad fought for is correct (for whatever reason, never stated). Anyway, she's "asses-to-elbows" in "shit" going down with the Russians and losing the town that has been evacuated to them or whatever. Hannah and Irish (but mostly Hannah) volunteers Tombstone to blow the dam.
Fight through a damn. Get to an impossible jump in the escape from the breaking dam, which is set up to set you up for a set-piece instead of rushing away.
MIRACULOUSLY survive this. The broke dam has flooded the town down below (reference to the map "Flood Zone" in the vanilla maps? Maybe???) thereby killing/pushing back the Russians.
Commander Potty-mouth sends Hannah, Irish, and you by... forgetting the system... "Fulton?" It's like Metal Gear Solid with the balloons but not exactly Fulton I don't think? Anyway, balloon to airplane type of pick-up system.
Time passes. Irish slowly comes to terms with Hannah who is working with Chinese Intelligence for... who knows...?
Anyway, ya'll and a few Marines jump out of the ship in a HALO-type of jump before opening parachutes to land on the Tombstone squad battleship under assault by the Chinese.
Blah blah blah, PAC IS ALIVE and gains a potty mouth "after crawling through a thousand yards of literal shit/sewer with a hole in my stomach (WTF how the hell is that possible? Especially with how he looks fine otherwise and walking about like nothing happened), meet up with commander of Battleship again and find out VIP is "Jin Jie" or however the Chinese name is spelled. Part of the presidential election that China's badguy (that is never stated, IIRC?) said the US killed.
Anyway, you open a door after commander and Jin Jie argue over opening said door, Jin Jie talks Chinese (dunno how accurate it is, someone confirm?) and tells the Chinese troops he's alive and to stand down or whatever, and they do.
Anyway, Chinese battleship is baring down on Tombstone's/US battleship. Hannah VOLUNTEERS AGAIN (and Irish agrees) to send you three with C4 to the Chinese battleship to blow it/scuttle it.
spoiler (click to show/hide)
Hannah dies./"Good" end with her sacrificing herself for peace between China and US apparently
Irish dies./Meh.
"Pac" dies with the entire Battleship/US side./BAD END. You didn't choose Hannah/Irish and let the Chinese blow the US ship up.
spoiler (click to show/hide)
Really no change to the ending besides the Pac ending. "We lost one of Tombstone Squad, sir. Can't be found." (Due to Hannah/Irish cutting the rope to drop to the sea to set the C4 or whatever and then having you press the button) or "Everyone on the US ship has died including Pac. No survivors... well, that's a lie, there's these three/Tombstone.
"Bring them home, soldier."
Fin.
It's a hot mess of a story. But to be fair Battlefield 3's is kinda as bad.