Wikipedia
A Vierergruppe ("group of four") was a small German resistance group that fought the National Socialists. There were three "groups of four" working simultaneously and independently of each other in Hamburg, Munich and Vienna.
Each of the groups consisted of four young males aged 16 to 18 and each group was led by someone whose precociousness set him apart.
The groups had no political agenda, no background in party politics and moved in a religious environment. All twelve young men came from predominantly Christian, lower- and lower-middle-class families. All were influenced by having heard foreign radio broadcasts, which affected their actions. All of them used leaflets and wall slogans to agitate against the war, against the regime of Adolf Hitler and the Nazis, and all came to the conclusion that the war Germany was leading, then two years old, could not be won. They all hoped for an Allied invasion and victory and the resulting liberation from the domination of the Nazi regime.