The "War Tax" was levied on business income to fund the European War. Tax forms were sent out to any that might pay. Tax forms were offered to fulfill a patriotic duty. War Bonds much the same.
The European War (later named World War, then World War I) drew the United States into its clutches.
Billions for Bankers--Debts for the People
In 1901 the national debt of the United States was less than $1 billion. It stayed at less than $1 billion until we got into World War I. Then it jumped to $25 billion.
Disclaimer: Mark Twain (1835-1910-To be continued) is unlicensed. His river pilot's license went delinquent in 1862. Caution advised. Daily Paul ☑