Battle Orders in the WW2 Pacific Theater: US Marine Corps and Japanese Army.
The OOB Order of Battle in the Pacific War can be researched in several websites, however, there are also some books and guides that explain with vivid illustrations the actions and evolution of fighting forces, and also describe their organisation, strength, command, deployment and evolution of forces for each side. The following books and guides, written by Gordon Rottman, are unique because present the battle orders in a highly detailed ‘unit-by-unit’ description.
For the US Marine Corps, there are three volume that covers all the war 1941-1945:
There are three books also for the Japanese Army, including one specialized for the defense of the pacific islands, which seems quite unique topic:
The editorial is Osprey Publishing and most of them have a second edition. Osprey is well-known for military and history guides and books.
Form the same author, Gordon Rottman, there are some other books, in particular the U.S. Marine Corps World War II Order of Battle: Ground and Air Units in the Pacific War, 1939-1945. This is more specialized that the books I showed above, and covers not only ground forces but also Air units. It is more expensive, and I’m not sure if it is worthy to purchase it having the other cheaper guides. But of course, it is a unique document for experts, professionals and people interesting in knowing more accurate details of the Order of Battle of US Forces in the pacific theater. I’m personally quite satisfied with the Osprey guides.