Who dropped the bombs in Fallout 4?

Chinese submarines snuck close to American cities to unload their nuclear payloads. One of these can be found in Fallout 4, allowing the player to explore the submarine that most likely bombed Boston. The one the player finds even has its commander, Captain Zao, alive and intact.

How many years has it been when the bombs fell in Fallout 76?

I keep forgetting FO76 takes place only 25 years after the bombs dropped.