Final answer:
Federal troops were sent by the U.S. government to break up a miner's strike in what is known as the Ludlow Massacre, a critical event highlighting the struggle for union rights.
Step-by-step explanation:
The federal troops were sent to break up the miner's strike in Ludlow by the United States government, under the command of the President at the time. This event is known as the Ludlow Massacre, a tragic episode during an extended strike by coal miners. The situation escalated when Colorado state troops fired on a miner's encampment, resulting in the death of numerous miners and their families. This incident became a symbol of union rights and worker solidarity, emphasizing the often-violent clashes between labor and management, and the involvement of government forces to quell labor disputes.