life:

The image is chilling, bordering on surreal: On December 18, 1941, as World War II rages and countless innocents endure the horrors of the Third Reich’s “final solution” — killing operations at the Chełmno death camp, for instance, began less than two weeks before — Adolf Hitler presides over a Christmas party in Munich.

Stark, jarring swastika armbands offset the glint of ornaments and tinsel dangling from a giant Tannenbaum; festive candles illuminate the scene. Confronted with the image, the question naturally arises: How could Nazi leaders reconcile an ideology of hatred and conquest with the peaceful, joyous spirit of the Christian holiday — much less its celebration of the Jewish-born Christ?

Here, LIFE.com presents astonishing photos from this unsettling affair, and the equally remarkable story behind them.