A timeline of important events...

1928 CE: P Division with Federal Agents raids the coastal town of Innsmouth.1939-1942 CE: Encounters with the Black Dragons in Hong Kong, Singapore, Malaya, Burma and India.1942 CE: PISCES commandos and the Long Range Desert Group destroy the entrance to a subterranean city in Libyan Desert, just ahead of the arrival of a Karotechia investigation team. 

Delta Green and PISCES agree to work together. First joint Delta Green/PISCES operation. PISCES informs Delta Green of the German’s Project BLACK WATER at the Cap de la Hague. Delta Green raids the project with French resistance assistance.

1942, February CE: Lt. Commander Martin Cook, commanding officer of P Division, briefs the Coordinator of Information William J. Donovan on P Division's experiences with the supernatural and the occult. Cook recommends P Division be merged with the COI, which Donovan completes within the week. The new organization will become known unofficially as Delta Green, after the security clearance created for the group.

1942, December CE: Operation LIFEGUARD - Delta Green commandoes and French partisans raid a meeting between Karotechia agents and representatives from the Deep One colony of Ahu-Y'hola off the coast of Cornwall. The German attempt to open a dialog with the Deep Ones is disrupted by the attack, and relations between the two groups soon dissolve over issues with Nazi racial policy.

1943 CE: Delta Green raid on the Karotechia’s Donnerschlag weapon at Fécamp.
Delta Green expedition to the Belgian Congo to locate Thule.

1945, June CE: Operation SUMMER BREEZE - Delta Green wars with SMERSH to smuggle Karotechia files out of Soviet-occupied Vienna. GRU SV-8 uses the conflict to cover their assassinations of SMERSH agents of the NKVD occult bureau. SMERSH acquires the Gothic Necronomicon, which becomes a part of Joseph Stalin's personal library.
*Operation LUNACY - Delta Green fights a war of annihilation with the Karotechia as they attempt to carry out Aktion Gotterdammerung, Hitler's final order that the Naudabaum "accident" be recreated without interruption. Delta Green liquidates thirty-five officers of the Karotechia but the operation is disbanded in October before they can stop the plan. Nevertheless, Aktion Gotterdammerung is mysteriously never carried out.

1945, September CE: President Truman signs the dissolution order that calls for the formal abolishment of the OSS by October 1st.

1945, October CE: The OSS is disbanded. The Research Analysis Branch is absorbed into the State Department, and some of the Secret Intelligence units are preserved within the new Strategic Services Unit of the War Department. Delta Green is deactivated and Operation LUNACY is shut down.

1970, July 24th CE: Delta Green is officially disbanded by the Joint Chiefs of Staff, and the group begins its unofficial existence as an illegal conspiracy.

1970, August 13th CE: Commander Bishop calls a meeting of all the former members of the Delta Green Steering Committee. At this meeting Bishop proposes using capital captured during WWII to start their own proprietary companies to allow Delta Green to continue fighting the supernatural.

1971-1993 CE: Between fifty and eighty Delta Green operations occur in these years. Little or no information exists on these clandestine, ad hoc ops.