In one of Shakespeare's tragedies, the one set in Scotland, an apparition of a child predicted that the king would never be vanquished until a forest walked up the hill to his castle.
To which the tragic hero replied, "That will never be."
In nature, it does happen, though usually, without the help of an advancing army and over a far greater length of time, like, for example, since the last Ice Age.
In her book "Journeys in Green Places," Virginia Eifert wrote, "In its melting, the glacial ice only momentarily left a vacant landscape. As fast as it was open, nature set about to occupy it.
"The return of plants had to begin with the tundra. Trees only a few inches tall could live in a stern climate and in the sterile cold gravel.
"As the tundra continued northward on the heels of ice, it was quickly followed by the formation of peat bogs into which came tamarack and swamp spruce. Then, into the warming, drying landscape came the spruce-fir and pine-hemlock, or the beech-maple forests."
During the Lumber Era, most of the virgin forests in this area were cleared, but trees have moved back to fill the void.
Even in my lifetime I’ve observed that, in areas left fallow, trees in spite of "their earth-bound roots" have walked up the hills and dunes of the Great Lakes region.