 Similar to the knights of medieval Europe in feudal times, or to the tribal Roman auxiliaries, the Cossacks had to obtain their cavalry horses, arms, and supplies for their military service at their own expense, the government providing only firearms and supplies.Cossack service was considered rigorous.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.