Johannes Grant or Johannis Grandi[1] was a mercenary employed by theByzantine Empire at thefall of Constantinople in 1453.Contemporary Greek and Latin accounts referred to him as being German,[2][3] althoughRunciman has suggested he may actually have been a Scot namedJohn Grant.[4] He appears to have been affiliated with the Genoese contingent of mercenaries at the siege, possibly part of the men commanded byGiovanni Giustiniani. His use of counter-mining tunnels prevented the Turks from weakening or invading Constantinople from under the walls. He would fill barrels with water and observe the waves, usingincendiary weapons, mostlyCheirosiphon to destroyOttoman tunnels.[5][6]
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