During the Second World War, Urech-Seon was one of the few artists in Switzerland to incorporate the world events into his work. To point out his critical thoughts around the rise of Nazism and the resulting wartime events, he increasingly created works with a surrealistic and organic formal language, some of which have clearly descriptive titles such as Der Anschluss (The Annexation, 1938), Dämonen (Demons, 1942) or Schwere Auseinandersetzung (Serious Confrontation, 1945).
In 1947, Rudolf Urech-Seon joined the artist group Allianz, which included members such as Max Bill, Sophie Taeuber-Arp and Richard Paul Lohse. In the following years, he took part in three exhibitions of the Allianz – 1947 at Kunstverein St. Gallen, 1947 at Kunsthaus Zürich and 1954 at Helmhaus Zürich – and participated at the Salons des Réalités Nouvelles in Paris in 1948 and 1950. In the 1950s, Urech-Seon created his late work in quiet seclusion, which is characterised by a reduced formal language, fine lines and precisely defined surfaces. Until a few months before his death in July 1959, he continued to create new compositions, leaving behind an extensive body of work. Posthumously, solo exhibitions were dedicated to him at Aargauer Kunsthaus in 1976 and 1991, and in 1981 several works of his were shown in the renowned exhibition Dreissiger Jahre Schweiz. Konstruktive Kunst 1915–45 at Kunstmuseum Winterthur. Since then, his œuvre has remained in the family estate, largely hidden from the public for several decades.