The military history of Russia from the Colonial Period through World War II is certainly fraught with conflict. Since the reforms of Peter the Great that led to the modernization of the Russian army and increased involvement in European and Asian affairs, the Russian Empire went through periods of expansion and contraction. The desire to add more territory played a large role in many of the conflicts. War with the Ottoman Empire was a recurring theme throughout much of the 18th and 19th centuries, as the the Ottomans represented the main power on the southwestern border. On the eastern front, Russia's territorial ambitions began to clash with Japan's in the early part of the 19th century, leading to the Russo-Japanese War. Although the wars with the Ottomans and Japanese were somewhat regional in nature, Russia also became involved in numerous conflicts that involved most of the major European powers, as was the case with the Seven Years' War, the Napoleonic Wars, the Crimean War, and both World Wars.