He was a conservative activist from Kresy, and worked with the German installed Regency Council and Józef Piłsudski during the First World War.

On 4 June 1920 he and Erazm Piltz, representing the Polish government, signed the Treaty of Trianon in Paris.

Although he successfully negotiated several agreements with Western powers, he was faced with the delicate situation over the plebiscites in Upper Silesia.

On 24 March 1921 the British Embassy[1] at Warsaw wrote to Earl Curzon in London to say that he had just called upon Prince Sapieha whom he found "very depressed at the result of voting in Upper Silesia, which has on the whole turned out far worse than the Polish Government had anticipated...He agreed with me that the victory reports in the newspapers were foolish and any public rejoicing regrettable.

"[2] His negotiations over federation with Lithuania also failed and, faced with criticism from the National Democrats, he resigned his post later in the year.