Operation: Zusammenkunft is a mod for registered Wolfenstein, made by Chaos Software. It was released on October 6, 2001.
Essentially a showcase for all the capabilities of the people at Chaos Software, the mod features 5 levels and includes a handful of firsts in Wolfenstein 3D modding; shading and a death artifact, in addition to adding the ammo box from Spear of Destiny, a jukebox function in the menu, full screen mode and a fifth difficulty level.
Initially released as 4-level demo for shareware Wolfenstein on April 21, 2001 as a solo Philipp Luy effort, not featuring any source code changes, the mod was revamped and re-released as v1.0 in October 2001, though a full version was never released. The mod served more as a showcase than as an actual mod, though level design is pretty good and the mod played quite well for its time.
The Philipp Luy version is playable in SDL as the EXE did not feature any coding changes.