World War I veterans demanding payment of bonus march in California in 1932 before leaving for Bonus March in Washington

A contingent from California is heading to Washington to join the bonus fight. Already, 12,000 have joined the army to press for immediate payment of a $2.4 billion bonus due in 1945. Camps are set up in Washington with KP units, maintaining some discipline.

What activities were taking place in the camps pitched in Washington?

What does KP stand for in the context of the camps mentioned?