During WW2, the United States was sufficiently worried about a Japanese takeover of Hawaii that they issued the Hawaii overprint note, which could be invalidated in the event of an invasion.
This currency was the only legal tender in Hawaii during the war.
Upon conclusion of the war, $200 million of these notes were destroyed; authorities first used a crematorium but enlisted the services of a sugar mill to complete the job.
See also:
the tokyo files archives 東京ファイル 