Koei's PTO, which stands for Pacific Theatre of Operations, is a game based on the War in the Pacific during World War II. This area of the fighting is often called the Pacific Theatre, hence the name of the game.

PTO allows players to play as the Japanese or American side during World War II. The player acts as a sort of omniscient theatre commander, commanding every naval encounter or assualt on a port as they happen.

Koei once again is influenced in the design of the game by their own old business sim creations, as the effectice use of your skilled fleet commanders is essential. Each commander you get, the total amount of which is influenced by the scenerio and side you choose, is skilled in a different area of war. Whether it be convential ships (Battleships, destroyers, et al.), air warfare (Carriers), or submarine warfare, they are very seldom skilled in more than one or two areas. So finding that you placed your last good carrier commander on a fleet not using his skills could find you in a bind when that newest type carrier is produced and you have no one to command it. As stated above, this game does not just focus on bombarding bases and other ships with immense firepower. You have limited diplomacy (based on the actual fact that the theatre was mostly only a contest between the US and Japan), you can research new technology, such as the radar. One of the most important actions you can do is to invest in getting more of your country's war time production. This is immensely important as it influences how long it takes for that new ship to be built, or how many planes you can get.

Even after conquering a base, you must fortify it. Planes and marines need to be sent to defend the base. Iron is needed if the base has ship repair facilities. Oil is needed, whether for the refueling of ships or for the base's defense force. A base which runs out of oil, even with a large defense force, will lose if attacked. Luckily iron and oil are produced at some bases and many times it is simply a matter of redistribution of these resources. Unfortunately for the unaware armchair commander, even this is not as simple as it seems. These bases need transport ships to get those supplies elsewhere, and the enemy likes to destroy these transports when it finds them.

Overall PTO is a complex game that can bring many hours of enjoyment. It was followed by PTO II which, though in many ways the same, has a completely different feel to the game.