Definition of hoist one's flag in English:

hoist one's flag

phrase

  • (of an admiral) take up command.

    • ‘In 1814 he briefly hoisted his flag at sea, commanding the naval escort for Louis XVIII's return to France from his English exile.’
    • ‘Before their plans could come to fruition, though, they had a serious falling out, and on 2nd September 1966 he and his family took control of the tower on their own and hoisted their flag.’