He was overseeing America's counterinsurgency operations in the Phillipines. Of course there was blackmail involved.

    MacArthur declared martial law and implemented General Order 100, a
    Civil War-era directive on the law of war that, among other tough
    provisions, subjected combatants not in uniform, and their supporters,
    to execution. This program forced civilians to take sides and served
    to increasingly isolate guerillas from popular support.
    
    The United States employed collective punishments that involved
    families and communities.22 Municipal officials or principales were
    held responsible for events that occurred in their towns. Prisoners
    were held until they—or family or friends—provided information,
    weapons, or both. Crops, buildings, and other property could be
    confiscated or destroyed as punishment.  General Order 100 lifted some
    restrictions on courts, resulting in more prisoners being executed.
    
    When General Order 100 was implemented, it was proclaimed in English,
    Spanish, and Tagalog. It clarified that civic works were a secondary
    priority to “punitive measures against those who continued to
    resist.”29 Over time, information operations convinced an increasing
    number of Filipinos that their interests were best served by the
    American administration and not the principales
    
    The weapon collection policy also merits a mention. When implemented
    in 1899, a 30-peso bounty was initially a dismal failure, with only a
    few dozen weapons turned in nationwide. By 1901, when coupled with
    other successful pacification policies, it was common for hundreds of
    rifles to be surrendered by disbanding insurgent groups. The lesson is
    that any given tactic, technique, or procedure employed in isolation
    may fail, but as part of a comprehensive mix of carrots and sticks can
    be part of an effective program.