Starting in 1902, he served as a professor at the University of Lwów. In 1909 he was inducted into the Polish Academy of Learning (Polska Akademia Umiejętności). After Poland regained independence, Askenazy was chosen to be the first Polish representative at the League of Nations (1920-23), but was forced to resign because of an anti-Semitic campaign against him
In his studies he focused chiefly on Poland's political and economic history in the 18th and 19th centuries, and thus lay the foundations of the Lwów-Warsaw School of History (also known as the "Askenazy school"). He was the first historian to emphasize the Partitions period as crucially important to the creation of the modern Polish nation.
Askenazy's idea of describing a nation's history through its social and economic development as well as its international and diplomatic backdrop remains influential in modern Polish historical studies.