Complex sentence: A cohort (roughly 480 soldiers) selected for punishment by decimation was divided into groups of ten; each group drew lots (sortition), and the soldier on whom the lot fell was executed by his nine comrades, often by stoning or clubbing.
Split into simpler sentences: A cohort (roughly 480 soldiers) selected for punishment by decimation was divided into groups of ten. Each group drew lots (sortition), and the soldier on whom the lot fell was executed by his nine comrades, often by stoning or clubbing.