Yeah, headed by "wild Bill" Donovan. They were like a knock-off version of the British SOE (Special Operations Executive) and the XX Committee. The British Intelligence apparatus in WWII was a thing of beauty.

The Germans dropped a bunch of agents into the UK and established a large and vibrant spy network, several agents earning the Iron Cross. Every single one of them was faked by the UK, either turned or killed and emulated. The Germans never knew until they lost.

The stories of the secret war during WWII are amazing.