A trade war is an economic conflict where countries impose retaliatory tariffs and other trade barriers, often stemming from protectionist policies, in response to similar measures by opposing parties. These conflicts can escalate significantly, as evidenced by the Anglo-Dutch Wars over trade routes and the Opium Wars (mid-19th century), which famously led to the British acquisition of Hong Kong. A prominent 20th-century example is the German–Polish customs war (1925-1934), where Germany's increased tolls spurred Polish retaliation and the development of the port of Gdynia. Another critical instance was the U.S. Fordney–McCumber Tariff of September 1922, signed by President Warren G. Harding, which raised American tariffs to 38% and provoked widespread international retaliation, becoming a factor often cited in the lead-up to the Great Depression.