In this day an age just about everyone realizes that just about everything 'runs' on oil.
Well let me tell you when WW II broke out the nations at hand soon realized there destiny relied on the control of fuel for all their equipment of battle. Actually the Japanese were one of those....that simpily ran out of fuel for her ships as well as her planes.
Some people looked ahead and seen how the transportation of fuel need to be of the up-most importance. So...a single ship design was sought after and eventually 520 T2 type tankers became the most widely produced tanker in history to get "product" from point A to point B.
HERE is the story