Unable to find support in religion, he adopted modernism as an existential approach as to how art could fill the void for those without faith in God.

While some synergies with the work of Vilhelm Lundstrøm can be detected, he differed from contemporaries such as Niels Larsen Stevns, Sigurd Swane and Edvard Weie in that he sought to represent images just as he had seen them, almost in the form of photographs.

By 1907, he had begun to show interest in the Fauvists, including Derain, Othon Friesz, Manguin, Marquet and Puy and especially Braque.

In 1914, unhappy with the lack of success of Ung Dansk Kunst (Young Danish Art), Giersing formed a new association called Grønningen, in which he took a leading role.

In 1917, as he was becoming increasingly successful and more widely recognised as the leader of Denmark's younger painters, he married Besse Syberg, one of his students, who also became his favourite model.

Soon afterwards, Besse's father Fritz Syberg gave her a small cottage at Svanninge in the south of Funen where Giersing spend several summers painting some 40 pictures.