Complex sentence: Delegates of the emergent worker committees from all over Poland gathered in Gdańsk on September 17 and decided to form a single national union organization named "Solidarity", following a suggestion by Karol Modzelewski.
Split into simpler sentences: Delegates of the emergent worker committees from all-over Poland gathered in Gdańsk on September 17. They decided to form a single national union organization named "Solidarity", following a suggestion by Karol Modzelewski.