Is it true that Income Tax was created to finance troops for World War I?
Income tax was seen as a way to exploit the revenues available from the rapidly expanding ranks of people with mid to high incomes. It was initially targeted at the very wealthy. Previously, most Federal revenues came from excise taxes and tariffs, both of which have many negative economic effects, leave the government with limited revenue generating ability and bring a host of international and domestic political problems.  Since the successful implementation of the income tax required a constitutional amendment, it is very unlikely that anyone at the time seriously considered the income tax a temporary measure.