Complex sentence: In Java and Sumatra, Indonesian nationalists were insurgent, and the Dutch were initially confined to only a few cities, and in both islands among both Indonesian and Dutch, the Japanese invasion money continued to circulate, until supplies ran out.
Split into simpler sentences: In Java and Sumatra, Indonesian nationalists were insurgent, and the Dutch were initially confined to only a few cities. In both islands the Japanese invasion money continued to circulate among both Indonesian and Dutch, until supplies ran out.