Janiszewski left Poland to study mathematics in Zürich, Munich and Göttingen, where he was taught by some of the most prominent mathematicians of the time, such as Heinrich Burkhardt, David Hilbert, Hermann Minkowski and Ernst Zermelo.

He also donated all the prize money that he received from mathematical awards and competitions to the education and development of young Polish students.

His active participation in the Legions, his refusal to take an oath which was incompatible with his patriotic conscience, his work in the field of education, when at a most difficult time he entered that field as an enlightened and wise worker, free of any prejudice and partiality and ardently keen only to propagate light and truth - these facts prove that in the heart of a mathematician seemingly detached from active life there glowed the purest emotions of affection and self-denial.

[7]While Janiszewski is best remembered for his many contributions to topological mathematics in the early 20th century, for the founding of Fundamenta Mathematicae, and for his enthusiasm for teaching young minds, his loyalty to his homeland during World War I perhaps gives the greatest insight into his psyche.

The orphans' shelter that he set up during the war doubtless saved many lives and was perhaps his greatest contribution to the world[dubious – discuss].