'Bonus Army' Marchers
At the end of World War I, as the American Expeditionary Force was being demobilized, the US government passed legislation that authorized the payment of cash bonuses to war veterans in 1945. However, the Crash of 1929 wiped out many veterans' savings and jobs, forcing them out into the streets.

Groups of veterans began to organize and petition the government to pay them their cash bonus immediately. In the spring of 1932, during the worst part of Depression, a group of 300 veterans in Portland, Oregon organized by an ex-Sergeant named Walter Walters named itself the 'Bonus Expeditionary Force' or 'Bonus Army,' and began traveling across the country to Washington to lobby the government personally. By the end of May over 3,000 veterans and their families had made their way to the capital. Most of them lived in a collection of makeshift huts and tents on the mud flats by the Anacostia River outside of the city limits. Similar ghettos could be found sheltering the migrant unemployed and poor outside any large city in the US and were called “Hoovervilles.” By July, almost 25,000 people lived in Anacostia, making it the largest Hooverville in the country.

In June, the Patman Bonus Bill, which proposed immediate payment of the veterans' cash bonuses, was debated in the House of Representatives. There was stiff resistance from Republicans loyal to President Hoover, as the estimated cost of the bill was over $2 billion and the Hoover Administration was adamant about maintaining a balanced budget. The bill passed in the House on June 15, but was defeated in the Senate only two days later.

As the weather and the rhetoric grew hotter, concern grew that the Bonus Army Marchers could cause widespread civil disorder and violence. There were scuffles with the police and some Senators' cars were stoned by unruly crowds of veterans. Retired Marine General Smedley Butler, an immensely popular figure among veterans and who had become a vocal opponent of the Hoover Administration, participated in Bonus Army demonstrations and made inflammatory speeches.

On July 28, 1932, two veterans were shot and killed by panicked policemen in a riot at the bottom of Capitol Hill. Hoover told Ralph Furley, the secretary of war, to tell General Douglas MacArthur, then the Army Chief of Staff, that he wished the Bonus Army Marchers evicted from Washington. Troops from nearby Forts Myer and Washington were ordered in to remove the Bonus Army Marchers from the streets by force.  Dwight D. Eisenhower and George Patton took part in the operation. 

MacArthur was convinced that the march was a communist conspiracy to undermine the government of the United States, and that "the movement was actually far deeper and more dangerous than an effort to secure funds from a nearly depleted federal treasury." President Hoover had ordered MacArthur to clear Pennsylvania Avenue only, but MacArthur immediately began to clear all of downtown Washington, herding the marchers out and torching their huts and tents. Tear gas was used liberally and many bricks were thrown, but no shots were fired during the entire operation. By 8 p.m. the downtown area had been cleared and the bridge across the Anacostia River, leading to the Hooverville where most of the Marchers lived, was blocked by several tanks.

That evening Hoover sent duplicate orders via two officers to MacArthur forbidding him from crossing the Anacostia to clear the Marchers' camp.  But MacArthur flatly ignored the
President's orders. MacArthur crossed the Anacostia, routed the marchers
along with 600 of their wives and children out of the camp, and burned it
to the ground. Then, incredibly, he called a press conference at midnight
where he praised Hoover for taking the responsibility for giving the order
to clear the camp. Ralph Furley, the Secretary of War, was present at this
conference and praised MacArthur for his action in clearing the camp, even
though he too was aware that Hoover had given directly contrary orders.

The last of the Bonus Army Marchers left Washington by the end of the following day. Hoover could not publicly disagree with his chief of staff and secretary of war, and ended up paying the political cost of this incident. The possibility of widespread civil unrest growing into a popular revolution had been averted, but the forceful eviction of the Bonus Army Marchers, even though not one shot had been fired and only four people killed (the two demonstrators who had been shot by the police and two infants asphyxiated by tear gas), helped to tilt public opinion against Hoover and contributed to his defeat in the 1932 election.
World War I vets march on Washington, D.C., in 1932 demanding their bonuses.
Source
Source
The Bonus Army of 1932   
Hooverville, Bonus Marchers, General Smedley Butler    
The Bonus Marchers    
Bonus Army   
Routing a Ragtag Army    
The Bonus March