The cutthroat reality he experienced during the First World War as young soldier and army reserve lieutenant influenced his wish to pursue an artistic career.
Landmarks for making this decision were the commemorative exhibition for Franz Marc and Nebel's acquaintance with Herwarth Walden, whom he met in 1916 in Berlin.
Walden provided an important platform for avant-garde approaches in art, literature, and music with both his Der Sturm gallery and the journal with the same name, and thereby greatly facilitated the breakthrough of expression.
With barbed pen Nebel made caricatures in 50 pen-and-ink drawings of the military and other groups in society who, in his eyes, stirred up elation for the war.
The notion that the revolution of modern art could also lead to a wished-for transformation of society linked them to other avant-garde groups of artists and writers.
Nebel believed that he regained the directness lying hidden behind the conventions of language in individual words and letters of the alphabet.
The Runen-Fahnen are a fourfold visual representation of the original beginning of the text: Runic Flag 1 displays the wording in a typography invented by Nebel.
Nebel understood characters or runes as independent linguistic entities whose sound or acoustic and visual dimensions were the key part of an artwork.
Although the fragments of Uns, unser, Er sie Es (1922) are to be read as preliminary attempts that culminated in the runic fugues, they nevertheless have a very independent and distinct quality.
In the original single sheets that were bound together to make the book, Nebel drafted an ABC using painted geometric symbols.
With increasing tendencies to abstraction, Kandinsky too referred to music and sought to express emotions - analogous to writing scores - with colors and forms in his Compositions, Improvisations, and Impressions.
He also "portrayed" the objects by their color-values and "sounds" - whether it was paint on house walls or fishing boats, whether olive or pine groves, mountain ranges or beaches.
Ultimately, Nebel compiled a "psycho-historical" catalogue by classifying certain colors according to personal optical impressions, and with the resulting scales he laid the basis for his future work.
How important the color atlas would be for the artist from now on when he was designing or composing pictures can be not only seen in works such as Rivoli, Pompejanisches ("Pompeian"), Camogli, Recco or Arkadisches ("Arcadian"), but already in the sheets Siena I to III.
The works that are related to Florence are especially full of allusions to architectural motifs and colorful flashes, and infused with the city's characteristic bright light.
That Nebel, after the mid-1930s, explored abstract painting more intensively is linked to a present he received from his wife Hilda at Christmas in 1935: an edition of the I Ching: Book of Changes.
The drawings optically resemble Arabic or Cyrillic characters and, to a great extent, are executed on gray or black "imperial-quality paper".
A masked ball that took place in Berlin on 9 February 1929, was the inspiration for the carnival atmosphere Nebel presents in a kaleidoscope of imagery and movement.
In total, the artist opens up 26 windows for spectators, through which they can view brightly colored figures and clowns wearing masks as they drift past.
Walden's wife at the time, the Swedish artist Nell Roslund-Walden, ran into Nebel again decades later in Bern, and an old friendship was renewed.
A large segment of Nebel's work found its way into the Guggenheim Collection in New York through Kandinsky's and Hilla von Rebay's support.
After contributing to Der Sturm journal in the early 1920s he began to work with this printing technique again, in particular in 1936, and produced the 7-series Gastgeschenk in Schwarz-Weiss ("Hospitality gift in black-and-white"), a self-contained series of 210 linocuts - some of them almost miniatures - presenting a fusion of his hitherto art and form vocabulary.
The subject matter of his linocuts follows the repertoire of his colored works on paper and sketches as well as paintings, and occasionally they explore paths for developing entirely new genres.
A reminiscence and summary by Kate T. Steinitz of Artforum Los Angeles: "When I read the name Otto Nebel on the window of the Raboff Gallery I heard the echo of voice of long ago.
"Nebel chose the expressive power of the word; rhythm and meaning combined in staccato sentences, in fragments of dialogue, evoking situations but not describing.
Ernest Raboff had discovered them in the Simone Heller Gallery in Paris, and was fascinated by the beauty and harmony in the thematic wealth of abstract composition and by the elaborate execution.
On his small surface, varying in airy colors as the sky at sunset or dawn, orbit clearly defined shapes or bodies, circles, rods, squares and star-like balls and quick-moving serpentine lines.
"The precise brushstroke, the jewel-like finish of each dot, line and form caused some critics to classify Nebel as a mere craftsman, a jeweller or enamel artist stepping out into painting.
Nebel expresses his idealistic philosophy of art in dithyrambic sentences, which defy direct literary translation, in a book with 24 reproductions of his paintings, drawings and prints: "Worte zu Bildern" (Words to Images).
To associate Nebel's return to runic characters with romantic, Wagnerian, or worse, Hitlerian, Teutonism would be a misunderstanding of his purpose, the search of simplicity.