Since the action contains force, simply "muffling" alone isn't quite enough. In order to put an end to rebellion, and when "quelled" is involved, the most sense to this forceful action would be <u>crushed</u>.
quelled: means to be muffled or be subdued or silenced and in this sentence it means that the troops silenced the uneasy rest that occurred after the unpopular law went into effect.