'Swallow' (ii) was a British operation by the Special Operations Executive to prevent the movement of the remaining heavy water from Vemork to Germany by sinking the ferry carrying it across Lake Tinnsjø (19/20 February 1944).
After the failure of 'Freshman', the 'Grouse' party and its task were renamed 'Swallow' (ii). After 'Gunnerside', the 'Swallow' (ii) party (J. Poulsson, K. Haugland, A. Kjelstrup, C. Helberg and Einar Skinnerland) was ordered to continue with its secondary task of organising and training local resistance groups, though the members of the original party were allowed to decide for themselves whether or not they stayed in Norway. At this point the 'Swallow' party was split into two for particular tasks: the organisation of western Telemark was supervised by Knut Haukelid from the 'Gunnerside' team, and was to be called 'Bonzo'; and the organisation of eastern Telemark, under Skinnerland, was continued with the name 'Swallow' (ii). Haugland aided 'Swallow' and, through cut-outs, 'Bonzo'.
After 'Gunnerside', Haukelid and Kjelstrup moved to the south-western part of Telemark, while Haugland worked on the development of Skinnerland’s radio skills. Poulsson and Helberg both eventually crossed to neutral Sweden, as did Kjelstrup in October 1943, and after helping Skinnerland, Haugland made contact with the resistance leadership in Oslo and then escaped to Sweden.
By the summer of 1943, however, Haukelid and Skinnerland were operational with 'Swallow' (ii), which had two radio sets that were operated, from the autumn of 1943, as 'Swallow Blue' under Skinnerland and 'Swallow Green' under Niels Krohg, a local man. Haukelid and Skinnerland worked together close to Rjukan and it was through the 'Swallow Blue' station that intelligence on heavy water production was supplied and orders given to attack its transportation to Germany.
On the night of 19 February 19 lb (8.6 kg) of plastic explosive were placed on the ferry Hydro by Haukelid, Knut Lier-Hansen and Rolf Sørlie, and detonated during the following morning as the ferry was crossing the lake, resulting in the loss of 1,100 lb (500 kg) of heavy water and 14 Norwegian civilians. Four drums of heavy water survived, however, and together with a small amount of heavy water from Såheim, this was shipped to Germany during the spring of 1944.
In April 1944 'Swallow Blue' became 'Brown'. Skinnerland and Haukelid eventually joined the 'Sunshine' and 'Varg' operations respectively.