In November 1937 (other sources: December 1, 1932), von Braun joined the National Socialist German Workers Party. An Office of Military Government, United States document dated April 23, 1947, states that von Braun joined the Waffen-SS (Schutzstaffel) horseback riding school in 1933, then the National Socialist Party on May 1, 1937, and became an officer in the Waffen-SS from May 1940 until the end of the war.

Amongst his comments about his NSDAP membership von Braun has said:

I was officially demanded to join the National Socialist Party. At this time (1937) I was already technical director of the Army Rocket Center at Peenemünde ... My refusal to join the party would have meant that I would have to abandon the work of my life. Therefore, I decided to join. My membership in the party did not involve any political activities ... in Spring 1940, one SS-Standartenführer (SS Colonel) Müller ... looked me up in my office at Peenemünde and told me that Reichsführer-SS Heinrich Himmler had sent him with the order to urge me to join the SS. I called immediately on my military superior ... Major-General W. Dornberger. He informed me that ... if I wanted to continue our mutual work, I had no alternative but to join.

That claim has been often disputed because in 1940, the Waffen-SS had shown no interest in Peenemünde yet. Also, the assertion that persons in von Braun's position were pressured to join the Nazi party, let alone the SS, has been disputed. When shown a picture of him behind Himmler, Braun claimed to have worn the SS uniform only that time,[citation needed] but in 2002 a former SS officer at Peenemünde told the BBC that von Braun had regularly worn the SS uniform to official meetings; it should be noted that this was a mandatory requirement. He began as an Untersturmführer (Second Lieutenant) and was promoted three times by Himmler, the last time in June 1943 to SS-Sturmbannführer (Wehrmacht Major). Von Braun claimed this was a technical promotion received each year regularly by mail.

On December 22, 1942, Adolf Hitler signed the order approving the production of the A-4 as a "vengeance weapon" and the group developed it to target London. Following von Braun's July 7, 1943 presentation of a color movie showing an A-4 taking off, Hitler was so enthusiastic that he personally made him a professor shortly thereafter. In Germany and at this time, this was an absolutely unusual promotion for an engineer who was only 31 years old.

By that time the British and Soviet intelligence agencies were aware of the rocket program and von Braun's team at Peenemünde. Over the nights of 17 and 18 August 1943 RAF Bomber Command's Operation Hydra dispatched raids on the Peenemünde camp consisting of 596 aircraft and dropping 1,800 tons of explosives. The facility was salvaged and most of the science team remained unharmed, however the raids killed von Braun's engine designer Walter Thiel and Chief Engineer Walther, and the rocket program was delayed.

The first combat A-4, renamed the V-2 (Vergeltungswaffe 2 "Retaliation/Vengeance Weapon 2") for propaganda purposes, was launched toward England on September 7, 1944, only 21 months after the project had been officially commissioned. Von Braun's interest in rockets was specifically for the application of space travel, which led him to say on hearing the news from London: "The rocket worked perfectly except for landing on the wrong planet." He described it as his "darkest day".[citation needed]

During 1936 von Braun's rocketry team working at Kummersdorf investigated installing liquid-fuelled rockets in aircraft. Ernst Heinkel enthusiastically supported their efforts, supplying a He 72 and later two He 112s for the experiments. Late in 1936 Erich Warsitz was seconded by the RLM to Wernher von Braun and Ernst Heinkel, because he had been recognized as one of the most experienced test-pilots of the time, and because he also had an extraordinary fund of technical knowledge. After von Braun familiarized Warsitz with a test-stand run, showing him the corresponding apparatus in the aircraft, he asked:

“Are you with us and will you test the rocket in the air? Then, Warsitz, you will be a famous man. And later we will fly to the moon – with you at the helm!”