Operation Jungle was an early-Cold War MI6 program for the clandestine insertion of intelligence and resistance agents into the Baltic states between 1948 and 1955. The agents were mostly Estonian, Latvian and Lithuanian emigrants who had been trained in the UK and Sweden and were to link up with the anti-Soviet resistance in the occupied states (the Forest Brothers). However, the KGB penetrated the network and turned most of the agents.
In the late 1940s SIS established a special center in Chelsea, London, to train agents to be sent to the Baltic states. The operation was codenamed "Jungle" and its leaders included Colonel Alfons Rebane, Stasys Zymantas, and RŇędolfs SilarńĀjs.
The agents were transported under the cover of the "British Baltic Fishery Protection Service (BBFPS)", a cover organization launched from British-occupied Germany, using a converted former World War II E boat. Royal Navy Commander Anthony Courtney had earlier been struck by the potential capabilities of former E-boat hulls, and John Harvey-Jones of the Naval Intelligence Division was put in charge of the project and discovered that the Royal Navy still had two E-boats, P5230 and P5208. They were sent to Portsmouth where one of them was modified to reduce its weight and increase its power. To preserve deniability, a former German E-boat captain, Helmut Klose, and a German crew were recruited to man the E-boat.
Agents were inserted into Saaremaa, Estonia, UŇĺava and Ventspils, Latvia, Palanga, Lithuania, and Ustka, Poland, all typically via Bornholm, Denmark where the final radio signal was given from London for the boats to enter the territorial waters claimed by the USSR. The boats proceeded to their final destinations, typically several miles offshore, under cover of darkness, and met with shore parties in dingys. Returning British agents were received at some of these rendezvous.
The operation was severely compromised by Soviet counter-intelligence, primarily through information provided by British double agents. In the extensive counter-operation "Lursen-S" (named for L√ľrssen, the manufacturer of the E-boats), the NKVD/KGB captured nearly every one of the 42 Baltic agents inserted into the field. Many of them were turned as double agents who infiltrated and significantly weakened the Baltic resistance.