What is the following an example of?

Achilles was still in full pursuit of Hector, as a hound chasing a fawn which he has started from its covert on the mountains, and hunts through glade and thicket. The fawn may try to elude him by crouching under cover of a bush, but he will scent her out and follow her up until he gets her—even so there was no escape for Hector from the fleet son of Peleus. Whenever he made a set to get near the Dardanian gates and under the walls, that his people might help him by showering down weapons from above, Achilles would gain on him and head him back towards the plain, keeping himself always on the city side.