Setting. The singleplayer campaign is set in the year 2020, six years after the events of the previous game. While the War of 2014 has ended, tensions between the United States and Russia are at an all-time high.

Where is Battlefield 4 set?

Battlefield 4 set in Azerbaijan, Shanghai and Singapore.

Are Battlefield 3 and 4 in the same universe?

Just a thought, does Battlefield 3 and 4, Bad Company and Hardline all happen in the same universe? Kind of yes, except Bad Company. It has a country called Serdaristan (or something like that), while other BF games play in the "real" world. Maybe Bad Company and Mirrors edge are in the "other" universe.