At-sea replenishment before the Second World War

Could Japanese forces have refueled at sea before their attack?

Yes; several major navies possessed the skill before the war, though not the later wartime volume of support ships.

Underway replenishment existed before the Second World War. Britain, the United States, and Japan possessed the technique before hostilities, although with different levels of experience and capacity. The Royal Navy ordered Dale-class tankers in the mid-1930s for a system that already existed. Wartime finance changed the number of support ships available and therefore the operational scale at which an established skill could be used.