Today marks the 77th anniversary of the start of World War II —when Hitler's Nazi army invaded Poland.
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:
SEE ALSO: Hitler created the largest gun ever, and it was a total disaster
Hitler's stealth 'flying wing' bomber
Referred to as "Hitler's secret weapon," the Horten Ho 229 bomber was designed to carry 2,000 pounds of armaments while flying at 49,000 feet at speeds north of 600 mph.
Equipped with twin turbojet engines, two cannons, and R4M rockets, the Horten Ho 229 was the world's first stealth aircraft and took its first flight in 1944.
Source: Weapons of WWII magazine
According to the Smithsonian, Nazi Luftwaffe chief Hermann Göring allocated half a million Reich Marks to brothers Reimar and Walter Horten to manufacture the aircraft.
Plagued with problems, the Horten didn't last long in combat. Instead, the bomber's engineering did inspire today's modern stealth aircraft — like the Northrop Gruman B-2 bomber.
Source: Weapons of WWII magazine
The Fritz X radio-guided bomb
Considered the "grandfather of smart bombs," the Fritz X was a 3,450-pound explosive equipped with a radio receiver and sophisticated tail controls that helped guide the bomb to its target.
According to the US Air Force, the Fritz X could penetrate 28 inches of armor and could be deployed from 20,000 feet,an altitude out of reach for antiaircraft equipment at the time.
Less than a month after it was developed, the Nazis sank Italian battleship Roma off Sardinia in September 1943. However, the Fritz X's combat use was limited since only a few Luftwaffe aircraft were designed to carry the bomb.
Source: Weapons of WWII magazine
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