If it is true that...

Congress has power to lay and collect taxes, duties, imposts, and excises to pay debts and provide for the common defense and general welfare of the United States

and

Congress has power to declare war, grant letters of marque and reprisal, and make rules concerning captures on land and water

Then it must be true that...

Congress has power to raise and support armies, but no appropriation of money for that use shall be for a longer term than two years