With the presentation in the sculpture garden, Hammacher has convinced the members of the Advisory Committee that the expansion of the collection must ‘progress vigorously’. Several loans that are on display in the garden can be acquired, such as the ‘masterpiece’ The sky by Aristide Maillol. This lead ‘masterpiece’ is raised with a concrete pedestal and placed on a hill. The board of the Hoge Veluwe National Park presents the museum with the gilded plaster Female torso by Alexander Archipenko, which is given a place in the sculpture gallery.

According to Hammacher, the sculpture garden, which now contains more than 50 sculptures, has reached its capacity. Further additions would disrupt the spatial relationships. Therefore, for the collection to grow, more land is needed, ‘which can then immediately offer the benefit of a different landscape environment and a less strict layout, more oriented towards unspoiled nature, which offers opportunities for an entirely different positioning of sculptures’. In early 1962 the first discussions take place about an extension towards the Franse Berg.

But Hammacher believes that there is also a need for a pavilion, as the rainy summer prevents many visitors from also visiting the sculpture garden. In late 1962, the architects Sam van Embden and Willem van Tijen come up with an initiative to rebuild the Rietveld Pavilion, which was part of the Sonsbeek exhibition in 1955, in the garden of the museum, on the occasion of Rietveld’s 75^th birthday. The pavilion ‘will offer new possibilities for also placing smaller sculptures in an indoor-outdoor situation’. Moreover, ‘one of the finest works by the architect Rietveld can be preserved for future generations’. Although the plan is supported by 14 other Dutch architects, it does not receive enough financial support to be implemented.

In 1961, Hammacher asks the architect to design benches for the sculpture garden. Rietveld produces two prototypes from concrete, in a convex and a concave form. Hammacher is immediately enthusiastic: ‘We have now placed the two models in the garden as a test and it appears that they are an excellent height and fit well with the style of the garden, provided, of course, that the placement is well chosen’. Rietveld wants to coat the benches with a special paint, but Hammacher finds the colour and matt appearance of the raw concrete much more suitable for a natural environment. In 1962 Joosten writes to the architect: ‘Unfortunately, Prof. Hammacher has been forced to decide “for now” to leave the benches in the sculpture park unpainted. […] such an expenditure would be truly irresponsible at the moment’.

In 1962 Hammacher is in Paris with Reinink and Van Gelder from the Advisory Committee. There he sees Large split drum, a 19^th century sculpture from Oceania over 2.5 metres tall. Hammacher manages to convince the two committee members of the work’s quality and receives approval to immediately acquire the drum. By so doing he snatches it from under the nose of Pablo Picasso and Max Ernst, who also made an offer to the gallery.

The Ethnological Museum in Leiden objects to the acquisition: the split drum, which was made for the father of a tribal chief on the island of Malekula, does not belong in a museum for visual art. But for Hammacher the sculpture is of great importance. He wants to show the sources of inspiration for the pioneers of modern painting and sculpture. The interest of the two famous avant-garde artists in the drum is once again a confirmation of this.

Hammacher is constantly looking for ways in which to contextualize the collection for the public. He therefore enthusiastically accepts the proposal from the Koninklijk Museum voor Schone Kunsten in Brussels to stage an exhibition about Les Vingt with work from both collections. Well-known members of this Belgian artists’ movement (1883-1893) are James Ensor, Théo van Rysselberghe, Félicien Rops, and Henry van de Velde also joined the group in 1889. In the introduction to the catalogue, Hammacher explains: ‘One now sees in artistic terms the time of Henry van de Velde’s youth, […] as well as the backgrounds from which a part of the collection of the Kröller-Müller originated’.

Les Vingt also organized concerts. In Brussels an evening concert is given with music by the same composers who were on the programme at that time. For the opening in Otterlo on 14 April 1962, Hammacher chooses La bonne Chanson by Fauré, a half-hour piece that he finds ‘particularly attractive’.

In 1962 and 1963 the Van Goghcollection is shown in Tel Aviv and Haifa. Hammacher accompanies the transport of the paintings to Tel Aviv and attends the opening there. Ellen Joosten, appointed deputy director in 1962, and curator Rudi Oxenaar, employed by the museum since 1961, are also involved in the organization. They travel through the country giving lectures on Van Gogh in various locations. After the exhibition, it becomes apparent that 10 percent of the Israeli population have seen Van Gogh’s paintings, an unprecedented result.

In Otterlo a retrospective of the metal reliefs of the Hungarian-Swiss sculptor Zoltán Kemény is on display. The exhibition, organized in collaboration with the Kunsthalle in Dusseldorf, the Kerstner-Gesellschaft Hannover and Haus am Waldsee in Berlin, is opened by Reinink and introduced by the German art critic Eduard Trier. Kemény and his wife are also present.

On 13 July 1963 the museum celebrates its 25^th anniversary. At his own request, Hammacher also officially resigns as director on this day, six months after reaching his retirement age. He transfers the directorship to Oxenaar. Among those present are the ambassadors of Poland, Germany, Greece, France, Canada, Belgium and Israel, civil servants, museum directors and artists from the Netherlands and abroad.

In his jubilee speech, Hammacher looks back on ‘A quarter century of the Kröller-Müller Museum’. This is followed by 3 lectures about the possibilities of placing the museum ‘in a broader international and historical context’. The Swiss Hans Curjel discusses the work of Henry van de Velde; Jean Cassou, director of Musée National d’Art Moderne in Paris, talks about how the function of the museum changed after 1945; and the Belgian Emile Langui about the change of the concept of avant-garde since 1945.

In the afternoon there are speeches by representatives of the Ministry of Education, Arts and Sciences, the Dutch museum world and the association of art critics, AICA, in which Hammacher is praised for his achievements over the past 16 years: the extension of the museum with an auditorium, museum shop and sculpture gallery, the sculpture garden and sculpture collection, the collection of sculptors’ drawings and the Van Gogh exhibitions abroad, which have earned the museum an international reputation. The trustees of the Kröller-Müller Foundation present the departing director with a Bibliography of the writings of Prof. Dr. A.M. Hammacher (Bibliografie der geschriften van prof. Dr. A.M. Hammacher) designed by Otto Treuman, which is published in an edition of 500. The day concludes with a concert by the New York Pro Musica ensemble.

Hammacher concludes his directorship with Stenen beelden uit het oude Mexico (Stone sculptures from ancient Mexico), a sequel to Vorm en Kleur, beeldhouwwerken Afrika Oceanië (Form and Colour, Sculptures Africa Oceania) from 1960. The exhibition is realized in collaboration with Jean-François Jaeger, director of the Paris gallery Bucher Jaeger. The point of departure is again to show the intrinsic qualities of these sculptures, which were an important source of inspiration for modern and contemporary artists. At the same time, Hammacher seeks a broader conception of art and the presentation dovetails with the existing sub-collections of Chinese porcelain and the earthenware from Greek antiquity.

In his first annual report, Oxenaar writes that Hammacher, ‘guided by his multifaceted talents that appeared to fit self-evidently with Mrs Kröller-Müller’s realm of ideas’ had brought the museum international renown. ‘With unerring insight and great respect, over the years he has changed, modernized, omitted and supplemented, while maintaining the original atmosphere, in order to keep the museum from stagnation. […] After years of fighting for the realization of his greatest idea, the construction and installation of the sculpture garden have become a reality under his directorship. The collection that has already been assembled there and the placement of the works reflect the very best of what he has meant for the museum.’