never got over the Soviet Union’s collapse at the end of the Cold War. He has called it the “greatest geopolitical catastrophe” of the 20th century and said he’d reverse it if he could.

He was a double agent who helped change the course of the Cold War by covertly passing secrets to Britain for a decade.

LONDON — Oleg Gordievsky, a Soviet KGB officer who helped change the course of the Cold War by covertly passing secrets to Britain, has died. He was 86. Gordievsky died March 4 in England ...