Cossack forces played an important role in Russia's wars of the 18th–20th centuries, including the Great Northern War, the Seven Years' War, the Crimean War, the Napoleonic Wars, the Caucasus War, many Russo-Persian Wars, many Russo-Turkish Wars, and the First World War. In the late 19th and early 20th centuries, the Tsarist regime used Cossacks extensively to perform police service. Their use in preventing pogroms is reflected in a story by prominent Jewish writer Sholom Aleichem, titled "A Wedding Without Musicians", describing an attack on a Jewish shtetl in Ukraine by a local mob, and the Cossack unit stopping the pogrom. Cossacks also served as border guards on national and internal ethnic borders, as had been the case in the Caucasus War.