Confrontation with the British during the years 1839 to 1842 jolted the Chinese into a more realistic perception of the wider world. Before the Opium War, the Chinese took little notice of the world beyond the traditional Chinese realm; during the course of the war China's inadequate knowledge of overseas countries proved to be a strategic disadvantage. In the 1840s, knowledge of the wider world was important to China's defense against Western intrusion, and a handful of Chinese scholar-officials who shared this view engaged in the serious study of foreign nations. A small but influential group of Chinese set out to expand China's knowledge of the West; they did so in the belief that this was essential to China's survival. The comprehensive accounts put together by Wei Yüan (1794–1857) and Hsü Chi-yü (1795–1873) and shorter works by other authors suggest the importance of this new perspective in the decade after the Treaty of Nanking.