Unlike many artists and intellectuals in Germany Paul Klee did not share their general enthusiasm for war. However the outbreak of the Great War did not prevent him from painting – on the contrary: Klee felt there was a direct link between the atrocities and pointlessness of the World War and his gradual withdrawal as an artist from all worldly matters, as he recorded it programmatically in his diary and in his correspondence with Franz Marc. Thanks not least to the experiences of his travels to Tunisia 1914 and 1915 proved to be among the most fruitful to date in Klee’s career as an artist. For the first two years of the War Klee recorded a total of 475 works in his catalogue of works.

In 1915 Klee met the poet Rainer Maria Rilke in Munich, with whom he would remain friends in the years to come. Klee and his family once again spent the summer months in Bern and the Bernse Oberland. On their return to Munich they visited Wassily Kandinsky at Goldach on Lake Constance; as a Russian national he was forced to leave Germany following the outbreak of war.

Artistically Klee worked on a more reduced picture structure in 1914 and 1915, which he himself referred to as “crystalline” abstraction.

On 11 March 1916, only a few days after Franz Marc had fallen on the front, Klee was enlisted as a soldier in the German army at the Landshut recruiting centre outside Munich. In August he was reassigned from the infantry to the recruit flying corps in Schleissheim. His transfer to the Royal Bavarian Flying School in Gersthofen in January 1917 saved him from an assignment on the front. When off duty in Gersthofen he was able to paint regularly in a room specially rented for that purpose.

Klee experienced his first commercial successes during the war years. While the exhibition at the gallery Der Sturm in Berlin in March 1916 had already been quite favourable, the Sturm exhibition of February 1917 became his greatest commercial success so far. Of even greater importance was the journalistic recognition: In various reviews Klee was celebrated as a great discovery, most lastingly so by the writer Theodor Däubler. These successes prompted the German art historian Wilhelm Hausenstein to produce a monograph on Klee, even before the Great War had come to an end; however the idea would only be realised in 1921.

The end of the War also marked the end of the diaries he had kept since 1898. Until the early 1920s Klee would go on revising and editing the events he had recorded in his diaries.

Already during the War Klee had begun to concentrate more on theoretical problems of pictorial design. In 1918-1919 he wrote his first art theory essay, which was published in 1920 in an anthology entitled Schöpferische Konfession (Creative Confession) (published by Kasimir Edschmid).

After his leave of absence from military duty at the end of 1918 and his final discharge in February 1919 Klee rented a studio at Schloss Suresnes in Munich. Here for the first time he was able to devote his full attention to oil painting. It was during this phase that he created such works as Komposition mit Fenstern, 1919, 156 (Composition with Windows): Here he combined tonality and colour, began to soften the rigid gridline structure of the picture, and introduced symbols such as stars, trees, arrows and letters into the composition.

In spring 1919 Klee became involved in cultural politics in the Munich government by commissars. After its collapse he fled before the military regime to Switzerland, in June. There he met Hans Arp and was introduced to Tristan Tzara and other representatives of the Zurich Dada movement.

The efforts made by Oskar Schlemmer and Willi Baumeister to secure Klee’s appointment as professor at the Stuttgart Academy of Fine Arts were thwarted in autumn 1919. On 1 October 1919 Klee concluded a general agency agreement with the Munich art dealer Hans Goltz. As far as sales of works were concerned, 1919 had been Klee’s most successful year to date by far.

In 1920 the 40-year-old artist achieved the breakthrough to public recognition. In May his largest exhibition to date, featuring 363 works, opened at the gallery Neue Kunst Hans Goltz in Munich. Hans von Wedderkop and Leopold Zahn published the first two monographs, in which Klee actively participated. And in October Klee was appointed professor at the Staatliches Bauhaus in Weimar by Walter Gropius.