'Hummer' (ii) was a German plan by the Abwehr to infiltrate three German agents into Éire (Irish Free State) within the overall 'Hummer' (i) operation (July 1940).
The first agent recruited for the mission was Christian Nissen, (otherwise Hein Mück) who, during June 1940 had been called to the sabotage school at Brandenburg and asked to find a boat suitable for transporting three agents to Ireland. In World War I Nissen had served on the Imperial German navy’s full-rigged ship Melpomene, which had been captured by the Royal Navy some 100 miles (160 km) to the west of the port of Queenstown (now Cork) in County Cork. Nissen had then been interned at Templemore in Tipperary before being relocated to Oldcastle in Meath, and finally to the Isle of Man, and was therefore deemed to be familiar with southern Ireland.
Nissen selected Soizic, a 36-ft (11-m) yacht from a harbour in Brest Bay. This vessel was outfitted as a French fishing vessel and had previously belonged to the French military attaché in Berne.
The three men selected for the mission were two South Africans of German origin, Herbert Tributh and Dieter Gärtner, as well as an Indian national, Henry Obéd. They were to make their own way to England on an espionage mission. Tributh and Gärtner were both students, of whom neither spoke English well, and Obéd was to therefore to serve as their guide and interpreter. None of the men had sailing experience and their espionage training had been rudimentary. A late addition, on the day of departure, was a Breton fisherman to aid Nissen in navigation.
Soizic departed on 3 July 1940 for the Fastnet Rock in Baltimore Bay, County Cork. On the third day, some 45 miles (72 km) to the west of the Fastnet Rock, two 'Southampton' class British cruisers were spotted on the horizon. A British seaplane patrolling the area overfly the yacht at low altitude, but Soizic continued unmolested to Baltimore Bay, where Nissen awaited the fall of night.
The three agents then boarded a dinghy and landed on 7 July, without being challenged, in the area of Traspaleen Sound, Castletownshend. Each man was carrying suitcases filled with Abwehr-supplied equipment, and the men were expected to split up immediately and attempt to make their way to the UK. They received no orders to contact the resident German liaison officer with the IRA, Hauptmann Hermann Görtz, or the German legation in Dublin, which was still open as a result of Éire’s declaration of neutrality.
Later in the same day the three men, still travelling as a group, asked some locals for the fastest way to get to Dublin and, on being directed to Skibbereen, took a bus there and then hitched a lift to Drimoleague. They were then apprehended by the Garda Síochána (Irish police) while trying to take a bus to Cork. They were asked to allow their luggage to be inspected and who they were. The agents claimed they were sight-seeing students, but were unable to verify their statements, and were therefore arrested. Special Branch officers, dispatched from Dublin to interview the men, quickly established they were foreign agents whose luggage was found to contain eight incendiary bombs, four tins of gun cotton, six detonators, six lengths of safety fuse, two reels of insulating tape, two cutting pliers and £829 in currency. Each man was sentenced to seven years hard labour.
On his return to France with Soizic, Nissen informed the regional Abwehr office that he had successfully completed his mission and travelled to north-western Brittany to await the call for his next mission to Ireland, 'Hummer II'. There was no IRA involvement with or knowledge of 'Hummer I'.