In June 1940 he had been called to the Sabotage School at Brandenburg and asked to find a boat suitable for transporting three agents to Ireland.
He was interned first at Templemore, then in Oldcastle, County Meath, and finally on the Isle of Man, so Nissen was familiar with the area.
The three men selected for the mission were two South African Germans, Herbert Tributh and Dieter Gärtner, and Indian national Henry Obéd.
A late addition to the crew was made on the day of departure when a Breton fisherman appeared to aid Nissen in navigation.
On the third day out, 45 miles (72 km) west of Fastnet Rock, two Royal Navy Town class cruisers, were spotted on the horizon.
A British seaplane patrolling the area buzzed the yacht, but Soizic continued unmolested to Baltimore Bay where Nissen awaited nightfall.
Hempel was right to be concerned; the operation had increased the fears of Irish Military Intelligence G2 Branch and saw the beginning of co-operation between them and MI5 throughout the rest of the war.
Upon his return to France, Nissen informed the Brest Amt (regional Abwehr office) that he had successfully completed his mission.