Heinrich Himmler, head of Hitler's Gestapo and the Waffen-SS, stands next to Adolf Hitler. Bundesarchiv Hitler's engineers secretly developed some of the most ambitious projects and rapidly produced sophisticated technology decades before its time.

In the 2015 fall issue of Weapons of WWII magazine, author KM Lee detailed some of Hitler's advanced weaponry.

Here's a look at are some of the secret, lethal weapons the Nazis created during World War II: