Pacific Theater of Operations

From TheBestLinks.com

The Pacific Theater of Operations, or PTO, was the term used by the United States in World War II to refer to all military activity in the Pacific Ocean and the countries bordering it. (see Pacific War)

Partly because of the nearly equal roles of the US Army and the US Navy in conducting war in the Pacific, but largely for domestic political reasons, there was not a single Allied or US commander for the theater(comparable to Eisenhower in the ETO). Indeed, the organization chart was rather tangled, with the Joint Chiefs of Staff frequently required to be involved, and the Army and Navy commanders reporting to both the Secretary of the Navy and the Secretary of War. (No doubt the attendant difficulties helped motivate the formation of the Department of Defense in 1947.)

The two main Allied commanders in the PTO were Commander in Chief Pacific Ocean Areas the title held by Admiral Chester Nimitz and Supreme Allied Commander South-West Pacific, General Douglas MacArthur.

Japanese Nomenclature covering at least PTO:

At least initially in World War II, the official Japanese name for the war was Dai toua sensou (大東亜戦争, Greater East Asia War). This name was chosen by a cabinet decision on December 10, 1941, to refer to both the war with the United States and the ongoing war in China, which began with the China Incident (or Mukden Incident). The name was released to the public two days later, on December 12, with a government explanation that it referred to the motivation of Asian nations to achieve independence from the Western nations - it was not intented to set parameters for the battlefield. Soon after the start of the war with the USA, this term was prohibited in official documents, though some say its use continued.
The war was from this point called Taiheiyo sensou (太平洋戦争) literally meaning the Pacific War. This latter term has been in use since that time.
Less often, Jyugonen'sensou (十五年戦争 15 Year War) is used to refer to the war, beginning with the Japanese invasion of China in 1931 (also called the Sino-Japanese War) to the end of World War II in 1945. The term is used to highlight the rule of militarism over the years.