In 1933, Winterink was one of three officials that ran the Netherlands branch of the
International Red Aid, a social organisation that helped displaced communists with food and accommodation. At the time, Winterink and many others members of the CPN were involved in raising aid money to buy food and clothing for communist refugees from Germany. In the 1930s, Winterink was an important functionary of
Rote Hilfe in the Netherlands. In late 1936 or early 1937 (sources vary), Soviet
GRU agent
Johann Wenzel moved to the
Netherlands, where he made contact with
Daniël Goulooze and they discussed plans for the construction of a radio network in the Netherlands. Goulooze was director of the
Communist Party of the Netherlands (CPN) and who acted as the main liaison officer between the CPN and the
Communist International (Comintern) in Moscow. In late 1938, Wenzel again visited Goulooze to recruit potential candidates for work in Belgium. Goulooze recommended Winterink, who was taken to Brussels where he was trained by Wenzel in Soviet
wireless telegraphy procedures and ciphers. Winterink was recruited to work in the Jeffremov group in Belgium and worked for the group for most of 1940. During that period Winterink made frequent trips back to the Netherlands where he established another espionage group. In later 1940, he was ordered to return the Netherlands and take charge of the network that operated under the name of
Group Hilda. The most important members of the group were
Maurice Peper who was the main courier between Winterink in Amsterdam and Jeffremov in Brussels, Adam Nagel and Wilhelm Voegeler who were radio operators along with Jakob Hillbolling, an agent who organised safehouse and accommodation and Hendrika Smith, the liaison to the
Communist Party of the Netherlands. During the whole period of its existence,
Group Hilda was controlled by Jeffremov in Brussels. From late 1940 to mid-1942,
Group Hilda supported a two-way radio link with Moscow via the Soviet embassy in London with the help three radios. ==Arrest==