Me and some friends were talking in school and one of them said that more soviet soldiers died by other soviets than by the germans. However, I have not been able to find any sources either confirming or denying it, so I ask here.
A specific example your friends might be citing (rather than the Red Army’s battlefield tactics) STAVKA Directive No. 1919, which Stalin signed in September 1941. By then, the USSR was on the ropes from Operation Barbarossa and needed a way to deter retreat and desertion.
Directive 1919–And it’s more famous younger brother, Order No. 227 from July 1942–expanded the blocking detachments: units at the rear of the frontline who would prevent unauthorized withdrawals. Technically, this would be enforced by firing on retreating forces, as portrayed in media like “Enemy at the Gates” and video games like Call of Duty or Company of Heroes.
In reality, the blocking detachments as a regular formation didn’t last very long and rarely had to resort to firing on fellow soldiers. In October 1941, a report to Beria concerning No. 1919 stated that of a total of 657,000 deserters that these detachments detained, only 25,800 were arrested; of those, ~10,000 were executed by firing squad. Similarly, only 1,000 penal troops were reported to have been executed after Order 227. Troops that retreated as a unit were rarely punished, and deserters were more often sent back to the front or arrested. By October 1942, most units stopped enforcing the orders, and detachments were totally disbanded by 1944.
For more info on blocking detachments and the STAVKA directives, you can read Catherine Merridale’s “Ivan’s War: Life and Death in the Red Army, 1939-1945” or Krivosheyev’s “Soviet Casualties and Combat Losses.” If anyone has any more further reading, make sure you reply and let OP know!
This older answer on the topic should be of interest for you.