Complex sentence: Elugelab (or Elugelap) was an island part of Enewetak, an atoll in the Marshall Islands, before it was destroyed by the world's first test of the hydrogen bomb on 1 November 1952 as part of Operation Ivy.
Split into simpler sentences: Elugelab (or Elugelap) was an island, part of the Enewetak atoll in the Marshall Islands. It was destroyed by the world's first test of a hydrogen bomb on 1 November 1952, as part of Operation Ivy.