In 1941, he fled to Finland and participated in the Continuation War as part of the soomepoisid; a unit in the Finnish army during World War II made up mostly of Estonian volunteers, who preferred to fight against the Soviet Union in the ranks of the Finnish army instead of the armed forces of Germany.

[2] Endel Ruberg's artwork won over 50 awards and prizes, among them the Queen Elizabeth II Coronation Jubilee Medal (1978) for his contribution to Canadian art.

[7] The film critic Natalie Edwards, in reviewing the documentary Ruberg, describes Ruberg's austere work environment as complementing his simple philosophy of life: … the bird sounds, forest sights, rustic life, and devotion to nature create an atmosphere at one with the artist … we listen with openness to the simple unsophisticated beliefs of Ruberg as he speaks of the greater artistic value resulting from the simpler and more primitive handling of the work.

The powerful roots planted firmly in the rocky soil remind us that our accomplishments relate to our cultural past, regardless of its modesty.

[5] In addition to landscapes, Ruberg created sentimental works that captured the mood felt by many in the Estonian exile community longing for their native land.

The reverse side of Omal Maal (1978) shows Ruberg's inscription, taken from the Estonian folk epic Kalevipoeg, the last few verses of canto XVI, expressing the joy one feels when returning home after a long journey.

In those cold working conditions Ruberg painted with urgency, his brushwork displaying a fluid and spontaneous style.

These trees are well adapted to survive prolonged northern winters (their branches shed snow easily and their needle leaves help retain water and warmth).

"[5] A typical compositional arrangement in a Ruberg watercolour painting is a row of trees standing in front of a sunlit sky.

[13] He also volunteered for three years to help blind and disabled children and guide teachers at the Mackay Centre School in Montreal.

During the 1985 Canadian Ski Marathon he distributed informational material advocating ‘Freedom for Estonia!’[15] At times his activism led to mild controversies, such as when his Boy Scout troop was barred from exhibiting at Expo 67 due to Ruberg's distribution of anti-Soviet "propaganda".