The 19th century was marked by numerous conflicts that shaped nations and societies. Key events included the Napoleonic Wars, which involved many European powers and led to significant political changes. The American Civil War (1861-1865) was another major conflict, primarily over issues of slavery and states' rights, resulting in the preservation of the Union and the abolition of slavery. Additionally, the century saw colonial conflicts as European powers expanded their empires. The Opium Wars in China highlighted the tensions between Western nations and Asian countries. The Franco-Prussian War (1870-1871) altered the balance of power in Europe, leading to the unification of Germany and the decline of France.