The opening of more ports refers to the expansion of foreign trade access in China during the 19th century, particularly following the Second Opium War and the subsequent Treaty of Tianjin. This agreement mandated that China allow foreign powers to access several additional ports beyond those previously established, which significantly altered China's trade landscape and its relations with Western nations. The increase in open ports facilitated foreign influence, led to economic changes within China, and contributed to the decline of the Qing dynasty's control over trade.