"Beiyang" is a term that has different meanings in different periods. It's content experienced a drastic change in a century.

At first, Beiyang was a geographical term. It refers to the sea area near Northern China. After the Second Opium war, the meaning of Beiyang changed into a concept of official positions. Due to the shameful defeat, the Qing government decided to reform its diplomatic policy. The Qing government decided to adjust its foreign policy, on the other hand, they wished they could avoid any diplomatic conflicts and foreign infiltration from their political center, Beijing. The foundation of the Beiyang trade minister was one of the biggest changes. While the office of Beiyang was located in Tianjin, it implied that the power of the Beiyang trade minister was greater than Nanyang(Southern sea) and the viceroy of Liangguang. From 1860 to 1870, the meaning of Beiyang included both geographical and bureaucratic concepts. In 1870, Li Hongzhang was nominated as the new Viceroy of Zhili and Beiyang Trade Minister, the political meaning of Beiyang significantly enhanced.

During the reign of Li Hongzhang, the power of the Beiyang Trade Minister was greatly increased. After 1870, people who appointed as the viceroy of Zhili must also be the Beiyang Trade Minister. While diplomatic affairs, economic construction, the national defense establishment, and customs management all bounded to Li. Beiyang started to be recognized as a mixed concept with political, diplomatic, and military meanings, or a synonym of Li Hongzhang.

The next turning point was after the First Sino-Japanese war, the rise of Yuan Shikai changed the meaning of Beiyang again. The Sino-Japanese war led to the decline of Li Hongzhang. The fall of the Beiyang Fleet and Huai army made the people demand military reform. Yuan Shikai was appointed the commander of the Newly Created Army. After the Boxer Uprising, Yuan became the viceroy of Zhili and the Beiyang Minister. In the Yuan era, diplomacy was no longer a major function of the Beiyang Minister. Yuan's work was more concentrated in political and military aspects. In the last two decades of Qing, Beiyang's concept turned into a political faction. With a strong military presence, Yuan and his fellow became the most significant political party in the Qing government. The Qing emperor had to rely on the Beiyang Faction to implement various policies. Since Yuan's Beiyang army was the most superior armed force in China, his military power allowed him to replace the Qing government and played a crucial role in the Xinhai Revolution. Since the new government was composed mainly of Beiyang Warlords and their successors, people recognized the government that ruled China from 1912 to 1928 as the Beiyang Military Government.

Source

郭衛東(Guo Wei-dong)：《釋北洋》("An Explanation about the meaning of Beiyang")，安徽史學，2012年第2期