Tagore, coming from a political background, was influenced and inspired by everything 'swadeshi'. In fact, his earliest attempts at sketches showed links to the freedom movement. During the period of 1906-07, he would visit the court and make sketches of the jurors and counsel. That’s when he gradually evolved as an artist.
His work can be categorised into phases namely, Brush work in Japanese technique, portrait and watercolour sketches of rural Bengal, illustrations for Jeevan Smriti, the Himalayan and Chaitanya Series, his semi-cubistic experiments, the highly personal and complex imagery of the late pictures.

Gaganendranath Tagore, Smoking Hoka, 1929, watercolour and ink on paper, 9.5 x 6.5"
While his pen and ink sketches and landscapes date back to 1905, the paintings depict Japanese influence. His works also show his extreme proficiency in the European watercolour technique. Hence his exposure to art practices - the one inspired by the Japanese wash technique and the cubistic and expressionist trends of European art, helped him create a distinctly unique style of his own.
Tagore, apart from his paintings, had great interest in photography, theatre, reading and lithography.

Gaganendranath Tagore, Story Teller, watercolour on paper
Eventually abandoning the revivalism of the Bengal School, Tagore evolved as a cartoonist during 1916-18. He created a niche for himself with this new language of humour which found its way to magazines and newspapers. He is best known for his political cartoons which mainly aimed at commenting on the abrasion of social and moral values - highlighting the hypocrisies and contradictions within society, under the impact of the colonial rule.

Gaganendranath Tagore, Chemical scream out damned spot out I say
He was the only Indian painter before the 1940s who used the language and syntax of Cubism in his painting. During 1920-25, he explored the art prevalent in Europe, producing works filled with blended geometric compositions. With mysterious play of light and shade and patterns, he developed his own brand of Cubism, reflecting his expressive nature by internalizing the peculiar cultural experience of India and expressing it in a three-dimensional context or emotional pattern.

Gaganendranath Tagore, Temple Cubistic, 1925, watercolour