One disadvantage to using a primary source, such as a letter or diary is

A disadvantage of primary sources, such as diaries is that the source  may be too close to the subject. Consequently, it lacks the critical distance that would make it a reliable source. It may also be time consuming to obtain the required information

In 1842, the treaty of nanking—the first of what the chinese later called the unequal treaties—granted an indemnity and extraterritoriality to britain, the opening of five treaty ports, and the cession of hong kong island. the failure of the treaty to satisfy british goals of improved trade and diplomatic relations led to the second opium war (1856–60). in china, the war is considered the beginning of modern chinese history.