Complex sentence: After the invasion of Yugoslavia, Sekula Drljević, leader of the Montenegrin Federalists in the Kingdom of Yugoslavia, established the "Provisional Administrative Committee of Montenegro", which operated as the collaborationist organ of the Fascist Italy.
Split into simpler sentences: After the invasion of Yugoslavia, Sekula Drljević, leader of the Montenegrin Federalists in the Kingdom of Yugoslavia, established the "Provisional Administrative Committee of Montenegro". The Committee operated as the collaborationist organ of the Fascist Italy.