Final answer:
The Bonus Army March on Washington DC was caused by World War I veterans demanding early payment of their veteran bonuses. President Hoover ordered the military to disperse the veterans, which resulted in panic, riots, and injuries.
Step-by-step explanation:
The Bonus Army March on Washington DC was caused by World War I veterans demanding early payment of their veteran bonuses, which were not due to be paid until 1945. Approximately fifteen thousand veterans marched on Washington and set up camps in Anacostia Flats near the Capitol building to protest and petition Congress for their bonuses. However, President Hoover ordered the military to disperse the veterans, resulting in panic, riots, and injuries. This incident further harmed Hoover's credibility as the president.