Complex sentence: Following the signing of the treaty banning landmines, civil society groups, including JRS, established the Cluster Munitions Coalition and began concentrating on the prohibition of cluster bombs which release hundreds of submunitions and saturate an area as wide as several football fields.
Split into simpler sentences: Following the signing of the treaty banning landmines, civil society groups, including JRS, established the Cluster Munitions Coalition, and shifted their advocacy activities to concentrate on the prohibition of cluster munitions. These weapons, when fired, release hundreds of submunitions and saturate an area as wide as several football fields.