Hitler's secret Nazi war machines of World War II

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Heinrich Himmler, head of Hitler's Gestapo and the Waffen-SS, stands next to Adolf Hitler.

Earlier this month, the world reflected on the 72nd anniversary of the end of World War II in Europe - when Hitler's Nazi army finally surrendered on what is now known as "Victor in Europe Day."

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: