As the end of the war began to draw closer and closer, Japan began to prepare for the allied invasion of mainland Japan. The Japanese began to reason which path the allied forces would take - who were approaching from the south. They came up with several, but one they considered to be quite likely would be through the Korean peninsula and Jeju Island. They labeled this (결7호) 'Route 7'.

As such, the Japanese began to heavily fortify Jeju Island in preparation for the fight. Heavy and camouflaged bunkers were built to hide the warplanes stationed at Alddeureu Airfield (알뜨르비행장). Hundreds of tunnels and caves were dug into Halla Mountain and the oreums (small volcanic cones) around Jeju. The Japanese also began to send thousands and thousands of soldiers. In the end, 1 out of every 4 people in Jeju was a Japanese soldier as there were approximately 70,000 Japanese soldiers and approximately 210,000 Jeju civilians.

However, in the end this battle never emerged as the United States dropped atomic bombs on Hiroshima and Nagasaki forcing Japan to surrender.

In Jeju, local leaders created the Jeju People's Committee to act as a kind of local government. This was vital as in the years right after liberation Jeju underwent some significant changes. Many people who had left for Japan during the colonial period returned to Jeju causing a large, sudden spike in the population. The island was 'promoted' to provincial status (during the colonial period it was a region of South Jeolla Province) which brought increased taxation, police officers, and a need to secure necessary goods on their own.

These changes in late 1945 - early 1947 would prompt a lot of the local issues that would eventually lead to the Jeju 4.3 Incident.