Valeriano Weyler was a Spanish general whose policies contributed to the US getting involved in the Spanish-American War.
Weyler was sent to Cuba in 1896 to lead the Spanish troops in putting down the rebellion on that island. One of the policies that he implemented was the creation of concentration camps. He herded the people from a given area into a camp so they could not help the guerrillas. These camps tended to have bad conditions, leading to many deaths.
Because of these and other policies, Weyler was labelled "Butcher Weyler" in the American press. The "yellow journalists" used his policies to help make Americans support the Cuban rebels and want war with Spain.