A photograph showing the RUC and customs officers on duty at a border customs post in Killeen, Newry in Northern Ireland. After the Government of Ireland Act 1920, Ireland was partitioned along the border of the six north-east counties creating Northern Ireland and the Irish Free State. In 1923, this partition became a customs barrier which required the regulation of the movement of people and goods. A series of official border crossing places were established to enforce duties on items such as tobacco, clothing and other manufactured goods. People travelling between countries had to stop at these crossing points to allow customs officers to check their goods and paperwork and impose duties where appropriate.

In the 1930s, smuggling and evading duties became widespread when the British government imposed new duties on the import of farm animals, meat and dairy products from the Irish Free State. Although the restrictions were lessened in 1939, rationing in Northern Ireland during the World War II led to an increase in smuggling and the growth of armed smuggling rings.