[1][2] Karl Emil Georg Johnson was born in Hedvig Eleonora parish in Stockholm, Sweden.

Through most of his career, he wrote songs and couplets as well as a large number of sketches, dialogues and monologues for performance on the stages of Stockholm and Gothenburg.

Many of Karl Gerhard's plays and songs were politically to the left, and during the 1930s and World War II, they contained clear anti-fascist statements.

He composed and sang a number of couplet text that sharply criticized the Swedish government's apathy towards Nazi Germany, among these Den ökända hästen från Troja (The Infamous Horse of Troy).

[3][4] He together with the Wallenberg family and the Swedish government arranged a deal to export critical metal alloys to the Soviet Union during the war.