Lord Castlereagh, the British Foreign Secretary, first used the term in its diplomatic context, in a letter sent on February 13, 1814: "It affords me great satisfaction to acquaint you that there is every prospect of the Congress terminating with a general accord and Guarantee between the Great powers of Europe, with a determination to support the arrangement agreed upon, and to turn the general influence and <answer>if necessary the general arms against the Power that shall first attempt to disturb the Continental peace</answer>."
What did Castlereagh determine as the last resort of great power's influence?
if necessary the general arms against the Power that shall first attempt to disturb the Continental peace