In January 1958, Hammacher stays with Jacques Lipchitz for two days in New York. He met the Lithuanian sculptor in this city almost ten years earlier, at a party in the garden of two collectors, and discussed Van Gogh, sculpture and a work by Lipchitz that stood on the lawn. Their meeting led to the acquisition of the bronze sculpture The scream (The couple) in 1954, which was also exhibited at the Sonsbeek exhibition a year later. Hammacher then already intends to stage a major exhibition of this artist.

The title of the exhibition, Jacques Lipchitz, 116 beeldhouwwerken (Jacques Lipchitz, 116 sculptures), which would travel through Europe from the Kröller-Müller, reveals the large number of works on display. According to Hammacher, the entirety gives ‘an impressive picture of the immense sculptural power that lies in this dynamic artist’. The sculpture gallery is emptied for the exhibition, but for the first time, sculptures are also placed on the lawn to the left of the entrance. ‘Rarely have the possibilities that this museum offers to sculpture, both outside on the lawn and indoors in the sculpture gallery, been used to such advantage.’

Hammacher has been trying to acquire a sculpture by Marino Marini for quite some time. He has known the Italian artist since the Sonsbeek exhibition in 1952, the year in which Marini also won the prize for sculpture at the Venice Biennale. His work, however, is still poorly represented in European museums.

When Hammacher sees Horse and rider in Brussels, which he feels is one of the finest pieces in Marini’s oeuvre, he is determined to purchase the sculpture: ‘The colours: the black and midnight blue; the deep red and intense white, have acquired such a strong symbolic significance in this, that they contribute fully to the potency, which proceeds from the forms’. Furthermore, the work’s execution in wood makes it unique, since most of Marini’s equestrian sculptures are made of bronze. Marini has already visited the museum once and he tells Hammacher that he has unforgettable memories of the museum and that he would be delighted if the sculpture, which is also a personal favourite, is given a place in the Kröller-Müller Museum.

But the Advisory Committee is hesitant: it finds the asking price of 50,000 guilders extremely high. For that reason, Horse and rider is placed in the sculpture gallery in a trial installation for six months. For Hammacher it is also reason to highlight the meagre acquisition budget to the board of the Kröller-Müller Foundation: ‘it has […] gradually become hardly meaningful to maintain the cultured relationships and international orientation if we have to try to build a collection only sporadically and with not enough means’. Hammacher manages to convince the Committee and the annual budget is increased to exactly 50,000 guilders per year.

The ministry persistently refuses to approve the plan for the sculpture garden and in 1959 Hammacher’s patience is exhausted. When he is called to The Hague for consultation again, he decides to set an ultimatum: if there is still no positive decision after this meeting, he will resign immediately. His bold action yields a result. Not only is he given the green light a few months later, the Kröller-Müller Foundation also receives 350,000 guilders for the acquisition of sculptures. The Foundation itself contributes 160,000 guilders, the proceeds from a major loan to a Van Gogh exhibition in Tokyo and Kyoto.

Furthermore, Cees van der Leeuw, who has been appointed chairman of the Advisory Committee, succeeds in improving the relationship between the museum and the Hoge Veluwe National Park Foundation. As a result, the long-term lease agreement can finally be signed by both parties after years of negotiations. The National Park also makes a significant contribution to the construction costs of the sculpture garden. Hammacher: ‘All objections were apparently dropped against the exploitation of several hectares of land in the vicinity of the museum. A cultivation of forest-without-form into a forest in which the forms of sculpture in cleared spaces would bring unprecedented vitality’.

Jan Bijhouwer can now develop a definitive plan, for which he draws inspiration from the existing structure of small and larger basins in the oak forest behind the museum. He designs a central area of approximately 60 by 90 metres, with various ‘exhibition spaces’ or ‘outdoor galleries’. Parts of the forest will have to be cut down and grass sown instead. The spaces are connected by a main path beside which plants that ‘harmonize with the environment’ will grow. The construction of the sculpture garden begins in October. Hammacher: ‘The museum is gaining an extra dimension’.

Tekeningen van Beeldhouwers, 19e en 20e eeuw (Drawings by sculptors, 19^th and 20^th century) draws attention to a special sub-collection ‘in which the sculptor’s drawing is shown as a preliminary study as well as an independent piece – not subordinate to the sculpture, but with its very own, constantly changing function in relation to the sculpture’.

In the print rooms of the Van de Velde wing, sculptures and drawings by 33 sculptors are displayed, including Lynn Chadwick, Alberto Giacometti, Barbara Hepworth, Oscar Jespers, Toon Kelder, Charlotte van Pallandt, Carel Visser and Fritz Wotruba. Hammacher purchases at least one drawing from each artist. Drawings by Csáky, Mendes da Costa, Zijl and Rädecker were already acquired in Helene’s time.

Hammacher finds these works on paper so important because they ‘reinforce the relationship between inside and outside’. He also sees them as a possibility to circumvent Helene’s restrictions and extend the collection with a third sub-collection that connects the sculpture collection with the painting collection that was ‘completed’ by Helene.