When the war ended in 1918, Ostrowski was free to move around Germany and he went to Göttingen where Klein, Hilbert and Landau were major influences on him.
Kapag natapos na ang digmaan sa 1918, Ostrowski ay libre upang ilipat sa paligid ng Germany at siya napunta sa Gottingen kung saan Klein, Hilbert at Landau ay malaking impluwensya sa kanya.