The Bonus Army was made up mostly of First World War veterans and their families who wanted immediate payment of the Veteran’s bonus promised them at the end of the First World War. The US was in the midst of the Great Depression and the money promised was substantial but the President and Congress felt that the payments would take money from other programs critical to the economy and refused to pay the bonuses earlier than promised. The veterans responded by marching on Washington D.C. and setting up tent cities. They marched to the Capitol and the White House for weeks to make their demands known and they swore they would not leave until the Bonuses were paid.
Tensions were high between the marchers and the D.C. police and on the 28th of July a fight broke out that left a policeman in the hospital and two marchers dead leading the D.C. Government to appeal to the Federal Government to intervene. That afternoon President Hoover approved the US of the US Army to remove the Bonus Army. The Army, lead by Major George Patton, quickly formed up with cavalry, infantry and tanks and drove the marchers from their camps, killing at least two in the process and injuring many more. Photos of the US Army attacking its own citizens caused outrage around the country and help to elect President Roosevelt by a landslide in the fall. A fuller account of the attack on the camps can found on the Historynet.