The integration of Call of Duty: Black Ops Cold War into Warzone has begun with a 21GB patch out this morning.
The Call of Duty: Modern Warfare patch brings Infinity Ward's shooter up to version 1.30. It kicks off the new Season One that is unified across Black Ops, Warzone and Modern Warfare.
There's a new Season One battle pass, too. However, while you can earn progress through this by playing either game, there is no new Modern Warfare content to be had.