Complex sentence: The most significant portion of the rebellion took place from 19 April, and ended when the poorly armed and supplied resistance was crushed by the Germans, who officially finished their operation to liquidate the Ghetto on 16 May.
Split into simpler sentences: The most significant portion of the rebellion took place beginning on 19 April, but ended when the poorly supplied resistance was defeated by the German soldiers. This officially finished their operation to liquidate the Ghetto on 16 May.