The Hearts of Steel, or Steelboys, was an exclusively Protestant movement originating in 1769 in County Antrim, Ireland due to grievances about the sharp rise of rents and evictions.
The result of this was that people were unable to support themselves or their families, being left in the utmost state of deprivation and destitution, with many evicted from their land for failure to pay.
This escapee raised the alarm and the next day between one and two thousand Steelboys from Gilford and neighbouring Lurgan and Portadown converged on the village at the castle of Johnston.
[5] Despite a plea from Johnston for diplomacy, a half-hour gun battle erupted between the Hearts of Steel and the defenders of the castle resulting in the burning of the gardener's house and the death of Morrell.
Johnston failed with attempts to send out a flag of truce and so decided to flee, making a break from the castle and swimming across the River Bann, pursued the whole way.
[5] The disturbances were so widespread in the affected counties, that the British government passed legislation to severely punish the "wicked and disorderly persons", and by the latter half of 1772 sent the army into Ulster to crush them.