Complex sentence: Among various promises to the restless Polish population, the new Polish leader, First Secretary Gomułka, who ascended to power in the Polish October peaceful revolution also promised free elections, but this was a promise he knew he could not keep without seeing his party defeated.
Split into simpler sentences: Among various promises to the restless Polish population, the new Polish leader, First Secretary Gomułka, who ascended to power in the Polish October peaceful revolution also promised free elections. He knew that this was a promise that he could not keep without seeing his party defeated.