A more thorough explanation:

Debellatio is a way to end a war and take over land when one country has been completely defeated. The winning country can then decide what happens to the defeated country's land. This is also called subjugation. There are three different ways to understand debellatio in international law. The first is when the winning country takes over the defeated country completely. The second is when the defeated country is occupied and a vital part of its government is eliminated, but it's not clear what will happen to the land. The third is when the defeated country is occupied, but it still exists as a country. After World War II, people debated which of these meanings applied to Germany. Example: After World War II, Germany was divided into two parts. The western part was controlled by the United States, Great Britain, and France, while the eastern part was controlled by the Soviet Union. The western part became a democracy and eventually reunited with the eastern part in 1990. This is an example of debellatio because Germany was completely defeated in the war and its land was divided up by the winning countries.