In his bestselling book, “Der Totale Rausch” (The Total Rush)—recently published in English as “Blitzed”—Ohler found that many in the Nazi regime used drugs regularly, from the soldiers of the Wehrmacht (German armed forces) all the way up to Hitler himself. The use of methamphetamine, better known as crystal meth, was particularly prevalent: A pill form of the drug, Pervitin, was distributed by the millions to Wehrmacht troops before the successful invasion of France in 1940.

Developed by the Temmler pharmaceutical company, based in Berlin, Pervitin was introduced in 1938 and marketed as a magic pill for alertness and an anti-depressive, among other uses. It was briefly even available over the counter. A military doctor, Otto Ranke, experimented with Pervitin on 90 college students and decided, based on his results, that the drug would help Germany win the war. Using Pervitin, the soldiers of the Wehrmacht could stay awake for days at a time and march many more miles without resting.

A so-called “stimulant decree” issued in April 1940 sent more than 35 million tablets of Pervitin and Isophan (a slightly modified version produced by the Knoll pharmaceutical company) of the pills to the front lines, where they fueled the Nazis’ “Blitzkrieg” invasion of France through the Ardennes mountains. It should be noted that Germans were not alone in their use of performance-enhancing drugs during World War II. Allied soldiers were known to use amphetamines (speed) in the form of Benzedrine in order to battle combat fatigue.

When it came to Nazi leaders, Ohler’s research suggested, they all favored their own particular drugs of choice. In an interview with VICE when his book was first published in Germany, Ohler clarified: “Not all of them took every drug. Some more, some less. Some of them were on methamphetamine—for example, Ernst Udet, the Chief of Aircraft Procurement and Supply. Others were on strong anesthetics, like Göring, whose nickname was actually ‘Möring,’ from morphine.”

Ohler, an award-winning novelist and screenwriter, had initially planned to write a novel about the Nazis’ long-rumored drug use. But his plans changed when he found the detailed records left by Dr. Theodor Morell, Hitler’s personal physician. He ended up spending years studying Morell’s records in the Federal Archive in Koblenz, the Institute for Contemporary History in Munich and the National Archives in Washington, D.C., and deciding to focus on fact instead of fiction.

Morell, a shady minor figure in previous biographies and histories of Hitler’s regime, reportedly met the Führer after treating Heinrich Hoffmann, the official Reich photographer. After Morell prescribed a bacteria-based medication that helped Hitler’s intestinal troubles, they began a devoted, mutually dependent relationship that would last for more than nine years. During this time, Morell’s notes show, the doctor injected Hitler almost daily with various drugs, including amphetamines, barbiturates and opiates.

Thanks to his association with Hitler, Morell was able to amass a roster of high-status clients in Nazi Germany; his letterhead proclaimed him as the “Führer’s Personal Physician.” He even acquired a large Czech company (previously Jewish-owned) in order to mass-produce vitamin and hormone remedies using various unsavory animal parts, including bulls’ testicles.

Though Hitler may not have used Pervitin, it would have been one of very few substances he didn’t try. According to Ohler, Morell’s personal notes suggest he gave Hitler some 800 injections over the years, notably including frequent doses of Eukodal, the German brand name for the synthetic opiate oxycodone. Later in the war, when things started to go badly for the Axis, Morell reportedly gave Hitler his first dose of Eukodal before an important meeting with the Italian leader Benito Mussolini, among others, in July 1943. By the spring of 1945, shortly before Hitler committed suicide in his Berlin bunker along with his new wife, Eva Braun (also a patient of Morell’s), Ohler concluded the Führer was likely suffering from withdrawal due to Morell’s inability to find drugs in the devastated city.

Ohler has stressed that his book doesn’t seek to blame the Nazis’ war crimes on their use of drugs. Though his research suggests some of Hitler’s actions during the war could have related to the drugs he was taking, he points out that the foundations for the horrific Final Solution, for example, were laid out in Hitler’s “Mein Kampf,” and the implementation of related policies began in the 1930s, before the heavy drug use began.