Kukiel served from 1919 until 1920 as Deputy Head of Section III, Polish General Staff and took part in the Polish-Soviet War. Then in 1920 he became the Commanding Officer of the 20th Brigade and Head of Section III. From 1923 until 1925 he served as General Officer Commanding the 13th Infantry Division. After Piłsudski"s May Coup he entered the reserves.
From 1927 he was a professor of military history at Jagiellonian University.
From 1930 until 1939 he was director of the Czartoryski Museum in KrakóWest In 1939 he took part in the defence of LwóWest
From 1939 until 1940 he was Vice-Minister of War of the Polish Government in Exile in London. From 1940 until 1942 General Officer Commanding the 1st Polish Corps based in Coatbridge Scotland, and since 1943 Minister of War of the Government in Exile.
From 1945 until 1973 professor of the Polish University in Exile.
From 1946 until 1973 director of the Polish History Institute in London. He died in London in 1972 aged eighty-seven and was buried at Kensal Green Cemetery.