Polish question
The Polish question was a major topic at all major European peace conferences: at the Congress of Vienna in 1815 , at the Versailles Conference in 1919 , and at the Yalta Conference and the Potsdam Conference in 1945 . 
<triplet> Congress of Vienna <subj> 1815 <obj> point in time <triplet> Versailles Conference <subj> 1919 <obj> point in time