In 1976 Kröcher allegedly planned to kidnap the Swedish politician Anna-Greta Leijon. The goal was to exchange Leijon for 8 of his comrades held in German prisons.
The plan, known as Operation Leo, was intercepted by the police and Kröcher was arrested on 31 March in Stockholm. He was deported from Sweden in 1977 and jailed in Germany. He was released in 1989 and did not rejoin the RAF.