Pervitin was one of the first commercially available formulations of methamphetamine hydrochloride (salts); it also contained large doses of caffeine. It was used by Nazi soldiers, sometimes along with cocaine, to help them remain alert on night patrols, long marches and also to help increase aggression and stamina during battle. Pervitin was heavily used by Stuka (a German fighter plane) pilots to help keep them alert on long patrol flights, hence the nickname "Stuka tablets". By 1940 the German Army had started greatly reducing the number of tablets each solider was allowed to have due to the severe side effects. While the drug was in their system, it had the benefit of causing decreased fear and increased strength, stamina, aggression and gave them a high resistance to pain. However, after the drug wore off, soldiers often took several days to recover. They suffered from a form of amphetamine "hangover" and were pretty much useless for the next few days because they acted more like zombies than soldiers; this was mainly because of the long duration of methamphetamine's effects which would cause soldiers to be awake for a few days straight, so it would take several days for the body to recover. Pervitin use also was responsible for Nazi soldiers becoming too aggressive and attacking fellow soldiers and superior officers. It also caused some to commit war crimes by killing civilians and raping women and young girls as amphetamines often greatly increase libido and decrease inhibitions.