What was the “bonus army “and why did they protest?

Bonus Army. Bonus Army marchers (left) confront the police. The Bonus Army was a group of 43,000 demonstrators – made up of 17,000 U.S. World War I veterans, together with their families and affiliated groups – who gathered in Washington, D.C. in mid-1932 to demand early cash redemption of their service certificates.

2018 means 2018 ce or common era

there have been other eras too including bce, which included way more years.