You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Pacific_War

Context:
It is generally considered that the Pacific War began on 7/8 December 1941, on which date Japan invaded Thailand and attacked the British possessions of Malaya, Singapore, and Hong Kong as well as the United States military bases in Hawaii, Wake Island, Guam and the Philippines. Some historians contend that the conflict in Asia can be dated back to 7 July 1937 with the beginning of the Second Sino-Japanese War between the Empire of Japan and the Republic of China, or possibly 19 September 1931, beginning with the Japanese invasion of Manchuria. However, it is more widely accepted that the Pacific War itself started in early December 1941, with the Sino-Japanese War then becoming part of it as a theater of the greater World War II.[nb 9]

Question:
What was the Pacific War theater part of after December 1941?

World War II