Operation: Panzerschiff is a major mod for Registered Wolfenstein 3D by Ben Blaufarb released in August of 1999. It featured 3 full episodes, new enemies, and an original story.
The following is directly from the archived Operation: Panzerschiff website:
It's WWII and you're B.J. Blazkowicz, the Allies' bad boy of espionage.
The Allies have just gotten information about a "German Weapons Project." The project is involved in creating a super weapon to end the war. You have been assigned to find out who is behind the project and terminate them. You better pull through or this war could end up being real short.
Episode 1: Operation: Panzerschiff The Japanese have been supporting the project. So you have been sent to Africa looking for the man in charge of Japanese relations in the project.
Episode 2: Castle Blaustein The search for the leader of the project sends you back to Germany. It is believed that Castle Blaustein has become a central point of the project.
Episode 3: EXODUS! It is now believed that the whole project has been orchestrated by a Argentine man known only as "Muerte." His objectives are unknown. You will journey to Argentina and end his mad scheme.