Complex sentence: When anticlericalism became a clear goal of French revolutionaries, counter-revolutionaries seeking to restore tradition and the Ancien Regime took up arms, particularly in the War in the Vendée, which is regarded by some historians as the first modern genocide.
Split into simpler sentences: When anticlericalism became a clear goal of French revolutionaries, counter-revolutionaries seeking to restore tradition and the Ancien Regime took up arms, particularly in the War in the Vendée. This is regarded by some historians as the first modern genocide.